Search

To investigate the effect of high‐energy X‐rays on site‐specific radiation‐damage, low‐dose diffraction data were collected from radiation‐sensitive crystals of the metal enzyme cytochrome c oxidase. Data were collected at the Structural Biology I beamline (BL41XU) at SPring‐8, using 30 keV X‐rays and a highly sensitive pixel array detector equipped with a cadmium telluride sensor. The experimental setup of continuous sample translation using multiple crystals allowed the average diffraction weighted dose per data set to be reduced to 58 kGy, and the resulting data revealed a ligand structure featuring an identical bond length to that in the damage‐free structure determined using an X‐ray free‐electron laser. However, precise analysis of the residual density around the ligand structure refined with the synchrotron data showed the possibility of a small level of specific damage, which might have resulted from the accumulated dose of 58 kGy per data set. Further investigation of the photon‐energy dependence of specific damage, as assessed by variations in UV‐vis absorption spectra, was conducted using an on‐line spectrometer at various energies ranging from 10 to 30 keV. No evidence was found for specific radiation damage being energy dependent. [ABSTRACT FROM AUTHOR]

Cytochrome c oxidase (CcO), the terminal oxidase in cellular respiration, couples proton pumping to O2 reduction. Mammalian CcO resides in the inner mitochondrial membrane. Previously, a model of H‐pathway proton pumping was proposed based on various CcO crystal structures. However, all previously determined structures were solved using crystals obtained at pH 5.7, which differs from the environmental pH of CcO in the inner membrane. The structures of fully oxidized and ligand‐free reduced CcO at pH 7.3 have now been determined. Structural comparison between the oxidized and reduced states revealed that the structural alterations that occurred upon redox change at pH 5.7 in Asp51, the magnesium‐containing cluster, haem groups and helix X, which provide important structural evidence for the H‐pathway proton‐pumping proposal, also occur at pH 7.3. These structural alterations were restricted to a local region of CcO; no domain movement was detected, nor were significant structural alterations detected in peripheral regions at either pH value. These observations indicate that the small and precise structural alterations that occur over the course of the reaction cycle are not affected by pH change, and that isolated CcO precisely performs proton pumping via the H‐pathway over a wide pH range. Because the pH is not uniform across the molecular surface of CcO, the fact that the overall structure of CcO is not affected by pH changes ensures the high enzymatic efficiency of this protein in the mitochondria. [ABSTRACT FROM AUTHOR]

Cytochrome c oxidase (CcO) couples proton pumping to O2 reduction. Its enzymatic activity depends sensitively on pH over a wide range. However, owing to difficulty in crystallizing this protein, X-ray structure analyses of bovine CcO aimed at understanding its reaction mechanism have been conducted using crystals prepared at pH 5.7, which is significantly lower than that in the cell. Here, oxidized CcO at pH 7.3 was crystallized using a fluorinated octyl-maltoside derivative, and the structure was determined at 1.77 Å resolution. No structural differences between crystals obtained at the neutral pH and the acidic pH were detected within the molecules. On the other hand, some differences in intermolecular interactions were detected between the two types of crystal. The influence of pH on the molecular surface is likely to contribute to the pH dependency of the aerobic oxidation of ferrocytochrome c. [ABSTRACT FROM AUTHOR]

Mitochondrial cytochrome c oxidase (C cO) transfers electrons from cytochrome c (Cyt. c) to O2 to generate H2O, a process coupled to proton pumping. To elucidate the mechanism of electron transfer, we determined the structure of the mammalian Cyt. c-C cO complex at 2.0-Å resolution and identified an electron transfer pathway from Cyt. c to C cO. The specific interaction between Cyt. c and C cO is stabilized by a few electrostatic interactions between side chains within a small contact surface area. Between the two proteins are three water layers with a long inter-molecular span, one of which lies between the other two layers without significant direct interaction with either protein. Cyt. c undergoes large structural fluctuations, using the interacting regions with C cO as a fulcrum. These features of the protein-protein interaction at the docking interface represent the first known example of a new class of protein-protein interaction, which we term 'soft and specific'. This interaction is likely to contribute to the rapid association/dissociation of the Cyt. c-C cO complex, which facilitates the sequential supply of four electrons for the O2 reduction reaction. [ABSTRACT FROM AUTHOR]

The X-ray structure of cyanide-bound bovine heart cytochrome c oxidase in the fully oxidized state was determined at 2.0 Å resolution. The structure reveals that the peroxide that bridges the two metals in the fully oxidized state is replaced by a cyanide ion bound in a nearly symmetric end-on fashion without significantly changing the protein conformation outside the two metal sites. [ABSTRACT FROM AUTHOR]

Key points Gap-junction (GJ) channels provide direct intercellular communication and are twice the length of most membrane channels, yet they often have high efficiency in permeation of ions, which is reflected by large unitary channel conductance (γj)., To reveal the key factors in determining the γj of a lens GJ channel, we studied connexin 50 mutant GJ channels, where a negatively or positively charged residue was introduced into a pore-lining domain., The results indicate that the pore surface electrostatic potential is a dictating factor for the connexin 50 GJ channel γj., A change in the local resistance of the channel pore associated with these mutant channels is an important factor for their voltage-dependent gating properties., The combination of dual patch clamp and homology structure modelling is a powerful approach in revealing molecular mechanisms of GJ gating and ion permeation., Abstract Gap-junction (GJ) channels are twice the length of most membrane channels, yet they often have large unitary channel conductance (γj). What factors make this possibly the longest channel so efficient in passing ions are not fully clear. Here we studied the lens connexin (Cx) 50 GJs, which display one of the largest γj and the most sensitive transjunctional voltage-dependent gating ( Vj gating) among all GJ channels. Introduction of charged residues into a putative pore-lining domain (the first transmembrane and the first extracellular loop border) drastically altered the apparent γj. Specifically, G46D and G46E increased the Cx50 γj from 201 to 256 and 293 pS, respectively and the G46K channel showed an apparent γj of only 20 pS. G46K also drastically altered Vj gating properties in homotypic G46K and heterotypic Cx50/G46K channels, causing an apparent loss of fast Vj-dependent gating transitions and leaving only loop gating transitions at the single channel current records. Both macroscopic and single channel currents of heterotypic Cx50/G46K channels showed a prominent rectification. Our homology structural models indicate that the pore surface electrostatic potentials are a dictating factor in determining the γj. Our data demonstrate, at the whole GJ channel level, a crucial role of the surface charge properties in the first transmembrane/first extracellular border domain in determining the efficiency of ion permeation and the Vj gating of Cx50 and possibly other GJ channels. [ABSTRACT FROM AUTHOR]

The vault particle, with a molecular weight of about 10 MDa, is the largest ribonucleoprotein that has been described. The X-ray structure of intact rat vault has been solved at a resolution of 3.5 Å [Tanaka et al. (2009), Science, 323, 384-388], showing an overall barrel-shaped architecture organized into two identical moieties, each consisting of 39 copies of the major vault protein (MVP). The model deposited in the PDB includes 39 MVP copies (half a vault) in the crystal asymmetric unit. A 2.1 Å resolution structure of the seven N-terminal repeats (R1-7) of MVP has also been determined [Querol-Audí et al. (2009), EMBO J. 28, 3450-3457], revealing important discrepancies with respect to the MVP models for repeats R1 and R2. Here, the re-refinement of the vault structure by incorporating the high-resolution information available for the R1-7 domains, using the deformable elastic network (DEN) approach and maintaining strict 39-fold noncrystallographic symmetry is reported. The new refinement indicates that at the resolution presently available the MVP shell can be described well as only one independent subunit organized with perfect D39 molecular symmetry. This refinement reveals that significant rearrangements occur in the N-terminus of MVP during the closing of the two vault halves and that the 39-fold symmetry breaks in the cap region. These results reflect the highly dynamic nature of the vault structure and represent a necessary step towards a better understanding of the biology and regulation of this particle. [ABSTRACT FROM AUTHOR]

To understand the basis for the lower activity of the tryptophan synthase β2 subunit in comparison to the α2β2 complex, we determined the crystal structures of apo-β2 and holo-β2 from Escherichia coli at 3.0 and 2.9 Å resolutions, respectively. To our knowledge, this is the first report of both β2 subunit structures with and without pyridoxal-5′-phosphate. The apo-type molecule retained a dimeric form in solution, as in the case of the holo-β2 subunit. The subunit structures of both the apo-β2 and the holo-β2 forms consisted of two domains, namely the N domain and the C domain. Although there were significant structural differences between the apo- and holo-structures, they could be easily superimposed with a 22° rigid body rotation of the C domain. The pyridoxal-5′-phosphate-bound holo-form had multiple interactions between the two domains and a long loop (residues 260–310), which were missing in the apo-form. Comparison of the structures of holo- Ecβ2 and Stβ2 in the α2β2 complex from Salmonella typhimurium ( Stα2β2) identified the cause of the lower enzymatic activity of holo- Ecβ2 in comparison with Stα2β2. The substrate (indole) gate residues, Tyr279 and Phe280, block entry of the substrate into the β2 subunit, although the indole can directly access the active site as a result of a wider cleft between the N and C domains in the holo- Ecβ2 subunit. In addition, the structure around βAsp305 of the holo- Ecβ2 subunit was similar to the open state of Stα2β2 with low activity, resulting in lower activity of holo- Ecβ2. Structured digital abstract • : Ecβ2 (uniprotkb: ) and Ecβ2 (uniprotkb: ) bind ( ) by x-ray crystallography ( ) • : Ecβ2 (uniprotkb: ) and Ecβ2 (uniprotkb: ) bind ( ) by biophysical ( ) [ABSTRACT FROM AUTHOR]

Intercellular signalling is an essential characteristic of multicellular organisms. Gap junctions, which consist of arrays of intercellular channels, permit the exchange of ions and small molecules between adjacent cells. Here, the structural determination of a gap junction channel composed of connexin 26 (Cx26) at 3.5 Å resolution is described. During each step of the purification process, the protein was examined using electron microscopy and/or dynamic light scattering. Dehydration of the crystals improved the resolution limits. Phase refinement using multi-crystal averaging in conjunction with noncrystallographic symmetry averaging based on strictly determined noncrystallographic symmetry operators resulted in an electron-density map for model building. The amino-acid sequence of a protomer structure consisting of the aminoterminal helix, four transmembrane helices and two extracellular loops was assigned to the electron-density map. The amino-acid assignment was confirmed using six selenomethionine (SeMet) sites in the difference Fourier map of the SeMet derivative and three intramolecular disulfide bonds in the anomalous difference Fourier map of the native crystal. [ABSTRACT FROM AUTHOR]

The binding of (+)-camphor to cytochrome P450cam (P450cam) expels a cluster of waters at the active site, raising the redox potential of the haem to an extent that allows reduction by the electron-transfer system. This binding was reported to involve no significant structural changes in the protein. Here, two ferric P450cam structures partially complexed with (+)-camphor were determined by X-ray crystallography at 1.30-1.35 Å resolution, revealing the structures of the substrate-free and substrate-bound forms. (+)-Camphor binding induces rotation of Thr101 to form a hydrogen bond that acts as a hydrogen donor to a peripheral haem propionate. This bonding contributes to the redox-potential change. [ABSTRACT FROM AUTHOR]

The structure of melon necrotic spot virus (MNSV) was determined at 2.8 Å resolution. Although MNSV is classified into the genus Carmovirus of the family Tombusviridae, the three-dimensional structure of MNSV showed a higher degree of similarity to tomato bushy stunt virus (TBSV), which belongs to the genus Tombusvirus, than to carnation mottle virus (CMtV), turnip crinkle virus (TCV) or cowpea mottle virus (CPMtV) from the genus Carmovirus. Thus, the classification of the family Tombusviridae at the genus level conflicts with the patterns of similarity among coat-protein structures. MNSV is one of the viruses belonging to the genera Tombusvirus or Carmovirus that are naturally transmitted in the soil by zoospores of fungal vectors. The X-ray structure of MNSV provides us with a representative structure of viruses transmitted by fungi. [ABSTRACT FROM AUTHOR]

Physarum polycephalum cytochrome b5 reductase catalyzes the reduction of cytochrome b5 by NADH. The structure of P. polycephalum cytochrome b5 reductase was determined at a resolution of 1.56 Å. The molecular structure was compared with that of human cytochrome b5 reductase, which had previously been determined at 1.75 Å resolution [Bando et al. (2004), Acta Cryst. D 60, 1929–1934]. The high-resolution structure revealed conformational differences between the two enzymes in the adenosine moiety of the FAD, the lid region and the linker region. The structural properties of both proteins were inspected in terms of hydrogen bonding, ion pairs, accessible surface area and cavity volume. The differences in these structural properties between the two proteins were consistent with estimates of their thermostabilities obtained from differential scanning calorimetry data. [ABSTRACT FROM AUTHOR]

All 13 lipids, including two cardiolipins, one phosphatidylcholine, three phosphatidylethanolamines, four phosphatidylglycerols and three triglycerides, were identified in a crystalline bovine heart cytochrome c oxidase (CcO) preparation. The chain lengths and unsaturated bond positions of the fatty acid moieties determined by mass spectrometry suggest that each lipid head group identifies its specific binding site within CcOs. The X-ray structure demonstrates that the flexibility of the fatty acid tails facilitates their effective space-filling functions and that the four phospholipids stabilize the CcO dimer. Binding of dicyclohexylcarbodiimide to the O2 transfer pathway of CcO causes two palmitate tails of phosphatidylglycerols to block the pathway, suggesting that the palmitates control the O2 transfer process.The phosphatidylglycerol with vaccenate (cis-Δ11-octadecenoate) was found in CcOs of bovine and Paracoccus denitrificans, the ancestor of mitochondrion, indicating that the vaccenate is conserved in bovine CcO in spite of the abundance of oleate (cis-Δ9-octadecenoate). The X-ray structure indicates that the protein moiety selects cis-vaccenate near the O2 transfer pathway against trans-vaccenate. These results suggest that vaccenate plays a critical role in the O2 transfer mechanism. [ABSTRACT FROM AUTHOR]

The absolute configuration of haem A, the prosthetic group of cytochrome c oxidase, was determined to be S by analysis of the bond angles surrounding the chiral centre of haem A after refinement with X-PLOR starting from respective initial structures with R and S configurations under absolute configuration constraints at 1.8 Å resolution. The same result was obtained by refinement at 1.8 Å resolution without the absolute configuration constraints. Both of these methods were applicable down to a resolution of about 2.8 Å. The constrained refinement converges more quickly than the unconstrained refinement. [ABSTRACT FROM AUTHOR]

Ab initio phasing by non-crystallographic symmetry averaging coupled with solvent flattening has previously been used to determine the structure of canine parvovirus [CPV; Tsao et al. (1992), Acta Cryst. A48, 293-301; Chapman et al. (1992), Acta Cryst. A48, 301-312]. As CPV particles were located at general positions, initial phases were generated with a spherical shell deviating from the centre of symmetry. In many virus crystals, the viral particles are located at positions with a centre of symmetry in the unit cell. Thus, the initial phases calculated with a spherical shell model have a centre of symmetry. The inherent difficulty in structural determination was breaking the centre of symmetry in the initial phase. The centric nature of the initial phases of the rice dwarf virus crystal, however, was successfully broken at low resolution by iteration of the density-modification method described by Tsao et al. (1992) [Naitow et al. (1999), Acta Cryst. D55, 77-84]. In this study, ab initio phasing was tested for seven viruses ranging from 82 to 344 Å in radius. Although the crystal structures of the initial spherical shell models for each virus had a centre of symmetry, the centric natures of the initial phases were successfully broken by non-crystallographic symmetry averaging coupled with solvent flattening at a low resolution; these phases were then successfully extended to high-resolution measurements. A novel procedure of ab initio phasing for spherical virus crystals is proposed. [ABSTRACT FROM AUTHOR]

Describes the scaling on one-shot oscillation images with a reference data set. Partialities and structure amplitudes of the reflections estimated using a least squares method to refine the scaling factor; Calculations showing that the reflection of the present crystal has a rocking curve that was steeper at the middle of profiles and more gradual at both ends of profile.

The X-ray structure of bovine heart cytochrome c oxidase solved for orthorhombic crystals showed a dimeric structure stabilized by four subunit-subunit contacts, namely, subunit Vb-subunit Vb on the matrix side, subunit I-subunit Vla, subunit Vla-subunit I in the transmembrane region and subunit VIb-subunit VIb on the intermembrane side. The same intermonomer contacts as in the orthorhombic crystals were observed in both hexagonal and tetragonal crystals, the X-ray structures of which were determined by the molecular-replacement method. These results suggest that the dimeric structure also exists under physiological conditions. These contacts, especially the subunit IVa-subunit I contact, in which the N-terminal portion of subunit IVa is placed on the surface of subunit I near the dioxygen-reduction site, indicate that the function of the bovine heart enzyme is likely to be controlled by perturbation of the monomer-monomer association. [ABSTRACT FROM AUTHOR]

Two azide ions were identified, one between the Fe and Cu atoms in the O2-reduction site and the other at the transmembrane surface of the enzyme, in the crystal structure of the azide-bound form of bovine heart cytochrome c oxidase at 2.9 Å resolution. Two geometries, a μ-1,3 type geometry between the Fe and Cu atoms and a terminal geometry on the Fe atom, are equally possible for an azide ion in the O2-reduction site. The other azide molecule was hydrogen bonded to an amide group of an asparagine and a hydroxyl group of tyrosine in a μ-1,1 type geometry. The antisymmetric infrared bands arising from these azide ions, which show essentially identical intensity [Yoshikawa & Caughey (1992), J. Biol. Chem. 267, 9757-97661, strongly suggest terminal binding of the azide to Fe. The electron density of all three imidazole ligands to CUB was clearly seen in the electron-density map of the azide-bound form of bovine heart enzyme, in contrast to the crystal structure of the azide-bound form of the bacterial enzyme [Iwata et al. (1995), Nature (London), 376, 660-669], which lacks one of the three imidazole ligands to CuB. [ABSTRACT FROM AUTHOR]

Membrane proteins invest the membranes of living cells and organelles with such functions as energy conversion, molecular transport and signal transduction. The number of known structures of membrane proteins is less than 20, which is too few to understand the highly organized biological reactions in a cell. The whole procedure including crystallization, for bovine heart cytochrome c oxidase is described as an example of crystal structural analysis of a membrane protein. Structural features of membrane proteins and structure-function relationships of the enzyme are also discussed. [ABSTRACT FROM AUTHOR]

We have analyzed the structure of mitochondrial cytochrome c oxidase in terms of general characteristics thought to be important for describing the architecture of helix bundle membrane proteins. Many aspects of the structure are similar to what has previously been found for the photosynthetic reaction center and bacteriorhodopsin. Our results lead to a considerably more precise general picture of membrane protein architecture than has hitherto been possible to obtain. [ABSTRACT FROM AUTHOR]

The article discusses an anomalous dispersion analysis of the mechanism of coupling the proton pumping process to the electron transfer reaction in resting-oxidized cytochrome c oxydase. The study suggests that peroxide moiety receives electron equivalents from cytochrome c without affecting the oxidation states of the metal sites. It further suggests that the metal site reduction is coupled to the proton pump.

The X-ray crystallographic structure of nitric oxide-treated bovine heart cytochrome c oxidase (CcO) in the fully reduced state has been determined at 50 K under light illumination. In this structure, nitric oxide (NO) is bound to the CcO oxygen-reduction site, which consists of haem and a Cu atom (the haem a3-CuB site). Electron density for the NO molecule was observed close to CuB. The refined structure indicates that NO is bound to CuB in a side-on manner. [ABSTRACT FROM AUTHOR]

L-Lactate oxidase (LOX) from Aerococcus viridans is a member of the α-hydroxyacid oxidase flavoenzyme family. An X-ray crystallographic study of a LOX mutant in which Arg181 is replaced by Met was initiated in order to understand the functions of the conserved amino-acid residues around the FMN in the enzyme active site. LOX-R181M crystals belong to the tetragonal space group I422, with unit-cell parameters a = b = 192.632, c= 200.263 Å, α = β = γ = 90°. There are four monomers in the asymmetric unit. Diffraction data were collected under cryogenic conditions to 2.44 Å resolution from LOX-R181M crystals at BL41XU, SPring-8. [ABSTRACT FROM AUTHOR]

Crystals of the drug-discharge outer membrane protein OprM (MW = 50.9 kDa) of the MexAB-OprM multidrug transporter of Pseudomonas aeruginosa have been grown at 293 K in the presence of 2-methyl-2,4-propanediol and a combination of surfactants. The crystal belonged to space group R32, with unit-cell parameters a = b = 85.43, c = 1044.3 Å. Diffraction data for OprM were obtained using the undulator synchrotron-radiation beamline at SPring-8 (BL44XU, Osaka University), which allowed an extra-long specimen-to-detector distance with a wide detector area. The crystal diffracted to 2.56 Å resolution using 0.9 Å X-rays from the synchrotron-radiation source. A heavy-atom derivative for isomorphous replacement phasing was obtained using iridium chloride. [ABSTRACT FROM AUTHOR]

Studies the crystallization and preliminary crystallographic analysis of rat monoamine oxidase A (MAO) complexed with clorgyline. Primary sequences but different substrate and inhibitor specificities in the two subtypes of MAO; Mechanisms underlying the unique substrate and inhibitor recognition.

The nuclear-transport protein importin-β mediates the nuclear import of the transcription factor SREBP-2 without requiring adaptor proteins such as importin-α, An importin-Β-SREBP-2 HLHZ domain complex was purified and crystallized. The crystals belong to space group P2[SUB1]2[SUB1]2[SUB1] and show diffraction to at least 3.0 Å resolution. The unit-cell parameters are a = 101.0, b = 113.2, c = 240.0 Å. Structure determination using the MAD or SAD method is under way. [ABSTRACT FROM AUTHOR]

Bacteriophage Mu baseplate protein gene product 44 (gp44) is an essential protein required for the assembly of viable phages. To investigate the roles of gp44 in baseplate assembly and infection, gp44 was crystallized at pH 6.0 in the presence of 20% 2-methyl-2,4-pentanediol. The crystals belong to space group R3, with unit-cell parameters a = b = 127.47, c = 63.97 Å. The crystals diffract X-rays to at least 2.1 Å resolution and are stable in the X-ray beam and are therefore appropriate for structure determination. Native data have been collected to 2.1 Å resolution using a DIP6040 image-plate system at beamline BL44XU at the SPring-8 facility in Japan. [ABSTRACT FROM AUTHOR]

Examines the optimization of the energy constant of the methionine S[sup delta]--C[sup epsilon]. Default value in X-ray protein structure refinement; Parameters of amino acid residues of bovine heart cytochrome; Deviation of bond lengths.

S-RNase is a 25 kDa pistil-specific protein associated with gameto- phytic self-incompatibility. The S-RNase is secreted into the transmitting tissue of the pistil and is responsible for the discrimination of pollen S-alleles. Crystals of Japanese pear S3-RNase were obtained by the hanging-drop vapour-diffusion method. Preliminary X-ray data showed that the crystals diffract to a 1.5 Å resolution and belong to the space group P21, with unit-cell parameters a = 45.4, b = 52.4, c = 47.4 Å, a = γ = 90, β = 106.5°. [ABSTRACT FROM AUTHOR]

The β-carbonic anhydrase from the red alga Porphyridium purpureum was heterologously expressed, purified and crystallized. The crystals belong to space group P21 (unit-cell parameters a = 63.8, b = 113.9, c = 73.8 Å, β = 104.1°) with two subunits per asymmetric unit and diffract to 2.5 Å resolution. [ABSTRACT FROM AUTHOR]

Fully oxidized cytochrome c oxidase (CcO) under enzymatic turnover is capable of pumping protons, while fully oxidized CcO as isolated is not able to do so upon one-electron reduction. The functional difference is expected to be a consequence of structural differences: [Fe(3+)-OH(-)] under enzymatic turnover versus [Fe(3+)-O(2)(2-)-Cu(2+)] for the as-isolated CcO. However, the electron density for O(2)(2-) is equally assignable to Cl(-). An anomalous dispersion analysis was performed in order to conclusively demonstrate the absence of Cl(-) between the Fe(3+) and Cu(2+). Thus, the peroxide moiety receives electron equivalents from cytochrome c without affecting the oxidation states of the metal sites. The metal-site reduction is coupled to the proton pump.

The X-ray crystallographic structure of nitric oxide-treated bovine heart cytochrome c oxidase (CcO) in the fully reduced state has been determined at 50 K under light illumination. In this structure, nitric oxide (NO) is bound to the CcO oxygen-reduction site, which consists of haem and a Cu atom (the haem a(3)-Cu(B) site). Electron density for the NO molecule was observed close to Cu(B). The refined structure indicates that NO is bound to Cu(B) in a side-on manner.

Vault is a 12.9 MDa ribonucleoprotein particle with a barrel-like shape, two protruding caps and an invaginated waist structure that is highly conserved in a wide variety of eukaryotes. Multimerization of the major vault protein (MVP) is sufficient to assemble the entire exterior shell of the barrel-shaped vault particle. Multiple copies of two additional proteins, vault poly(ADP-ribose) polymerase (VPARP) and telomerase-associated protein 1 (TEP1), as well as a small vault RNA (vRNA), are also associated with vault. Here, the crystallization of vault particles is reported. The crystals belong to space group C2, with unit-cell parameters a = 708.0, b = 385.0, c = 602.9 angstroms, beta = 124.8 degrees . Rotational symmetry searches based on the R factor and correlation coefficient from noncrystallographic symmetry (NCS) averaging indicated that the particle has 39-fold dihedral symmetry.

Hepatitis E virus (HEV) accounts for the majority of enterically transmitted hepatitis infections worldwide. Currently, there is no specific treatment for or vaccine against HEV. The major structural protein is derived from open reading frame (ORF) 2 of the viral genome. A potential oral vaccine is provided by the virus-like particles formed by a protein construct of partial ORF3 protein (residue 70-123) fused to the N-terminus of the ORF2 protein (residues 112-608). Single crystals obtained by the hanging-drop vapour-diffusion method at 293 K diffract X-rays to 8.3 A resolution. The crystals belong to space group P2(1)2(1)2(1), with unit-cell parameters a = 337, b = 343, c = 346 A, alpha = beta = gamma = 90 degrees , and contain one particle per asymmetric unit.

Physarum polycephalum cytochrome b(5) reductase catalyzes the reduction of cytochrome b(5) by NADH. The structure of P. polycephalum cytochrome b(5) reductase was determined at a resolution of 1.56 A. The molecular structure was compared with that of human cytochrome b(5) reductase, which had previously been determined at 1.75 A resolution [Bando et al. (2004), Acta Cryst. D60, 1929-1934]. The high-resolution structure revealed conformational differences between the two enzymes in the adenosine moiety of the FAD, the lid region and the linker region. The structural properties of both proteins were inspected in terms of hydrogen bonding, ion pairs, accessible surface area and cavity volume. The differences in these structural properties between the two proteins were consistent with estimates of their thermostabilities obtained from differential scanning calorimetry data.

Monoamine oxidase (MAO) is an FAD-containing mitochondrial outer-membrane protein which catalyzes the degradation of several neurotransmitters in the central nervous system. The two subtypes of MAO, MAOA and MAOB, have similar primary sequences but different substrate and inhibitor specificities. The structure of human MAOB has recently been determined, but the structure of MAOA remains unknown. To clarify the mechanisms underlying their unique substrate and inhibitor recognition and thereby facilitate the development of new specific inhibitors to treat MAO-related neurological disorders, rat MAOA was crystallized in a complex with the specific inhibitor clorgyline. Diffraction data were collected to 3.2 A resolution. The crystal belongs to the space group P4(3)2(1)2, with unit-cell parameters a = b = 158.2, c = 258.4 A.