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The transcriptional coactivator p300 binds to and mediates the transcriptional functions of the tetrameric tumor suppressor p53. Both proteins consist of independently folded domains linked by intrinsically disordered sequences. A well studied short sequence of the p53 transactivation domain, p53(15-29), binds weakly to four folded domains of p300 [Taz1/cysteine-histidine-rich region 1 (CH1), Kix, Taz2/CH3, IBiD], with dissociation constants (KD) in the 100 [micro]M region. However, we found that a longer N-terminal transactivation domain construct p53(1-57) bound tightly to each p300 domain. Taz2/CH3 had the greatest affinity ([K.sub.D] = 27 nM) and competes with the N-terminal domain of Mdm2 for the p53 N terminus, p300 thus can protect the N terminus of p53 against the binding of other proteins. Mutations of p53 that abrogate transactivation (L22Q/W23S, W53Q/F54S) greatly weakened binding to each p300 domain, linking phenotypic defects to weakened coactivator binding. We propose a complex between tetrameric p53 and p300 in which four domains of p300 wrap around the four transactivation domains of p53. AD1 | cAMP response element binding protein-binding protein | IBiD homology domain | Mdm4 I SRC-1

The characterization of enzymatic activities and crystal structure of an archael acylphosphatase is reported. The data suggests that, while putative acylphosphotase is less efficient than other mammalian homologues at 25 degree celsius, the thermophilic enzyme is fully active at the optimal growth temperature of Pyrococcus hirokoshii.

Research has been conducted on the C-type lectin TC14. The dynamic properties of this lectin have been investigated via the measuring the (super)15 N longitudinal and transverse relaxation rates and the heteronuclear NOEs.

Saccharomyces cerevisiae Elongin C, an essential part of the mammalian CVC(VHL) E3 ubiquitin ligase complex, has been characterized from the perspective of biophysics. Findings show it likely interacts with various target proteins including the VHL protein by an induced-fit mechanism that involves the conformationally flexible carboxy-terminal helix 4. The VHL gene is mutated in the von Hippel-Landau disease and its familial cancer syndrome and in some spontaneous malignancies. Binding of a peptide representing the major ELC binding site of the VHL tumor suppressor protein almost eliminated chemical exchange processes but brought on substantial conformational changes in Elc1 that lead to pronounced rotational anisotropy.

The structure of the S1 RNA-binding domain from the Escherichia coli polynucleotide phosphorylase was determined by nuclear magnetic resonance spectroscopy. It is composed of a five-stranded antiparallel beta barrel. Conserved residues on one face of the barrel and adjacent loops form the putative RNA-binding site. The structure of the S1 domain is very similar to that of cold shock protein. Enhanced sequence searches indicated unknown S1 domains in RNase E, RNase II, NusA, EMB-5 and other proteins.

Multinuclear NMR experiments and 3-D backbone triple-resonance experiments help examine the folding pathway of barnase and active complete backbone 13C, 15N and 1H NMR assignments for barnase unfolded at 30 degrees Celsius and pH 1.8. Analysis of NMR data proves the presence of small areas of stable residual structure in the pH-denatured form of barnase. The stable residual structure is significant in regions containing Gly-9-Tyr-17 and Asp-93-Tyr-97 and the docking of these regions determines the rate of folding.

The structure of barstar, determined through 13C/15N doubly labeled samples using heteronuclear NMR techniques, allows the resolution of several inter-side-chain NOEs that are essential to describe the relative positions of the helices. The protein consists of three parallel helices, one poorly defined helix and three-stranded parallel beta-sheets. The heteronuclear techniques characterize the nature of the acid-denatured state of barstar that has the properties of a molten globule state.

Heteronuclear 2D and 3D NMR spectroscopy is employed to examine the binding of 3'-MP to the ribonuclease, barnase. Inter- and intramolecular NOEs are recognized by employing 2D and 3D NOESY spectra. The measurement of a solution conformation for the geometries reveals the well-defined location of the guanine ring of the ligand. The NM protons of Ser57 Arg59 are used by the guanine ring to produce hydrogen bonds. The microbial guanine-specific ribonucleases reveal the preservation of a loop where the residues are positioned.

The structural analysis of AF2198, a Jab1/MPN protein domain from Archaeoglobulus fulgidus, reveals that Rpn 11 is the component of the 26S proteasome mediating deubiquitination of protein substrates.

Results reveal that the thermal stability of Themococcus celer ribosomal protein L30e is attributed to the near neutrality of the overall charge due to acidic residues in place of polar residues. The protein exhibits extensive ion pair networks on the molecular surface with a reduction in the exposed nonpolar surface areas and the side chain atoms form hydrogen bonds with main chain atoms.

c‐MYC and the SWI/SNF chromatin remodeling complex act as master regulators of transcription, and play a key role in human cancer. Although they are known to interact, the molecular details of their interaction are lacking. We have determined the structure of the RPT1 region of the INI1/hSNF5/BAF47/SMARCB1 subunit of the SWI/SNF complex that acts as a c‐MYC‐binding domain, and have localized the interaction regions on both INI1 and on the c‐MYC:MAX heterodimer. c‐MYC interacts with a highly conserved groove on INI1, while INI1 binds to the c‐MYC helix‐loop‐helix region. The binding site overlaps with the c‐MYC DNA‐binding region, and we show that binding of INI1 and E‐box DNA to c‐MYC:MAX are mutually exclusive. c‐MYC interacts with the INI1/hSNF5/BAF47/SMARCB1 subunit of the SWI/SNF chromatin remodeling complex. We have determined the structure of INI1 RPT1 that acts as a c‐MYC‐binding domain, and localized the interaction regions on both INI1 and the c‐MYC:MAX heterodimer. The binding site overlaps with the c‐MYC DNA‐binding region. We show that binding of INI1 and E‐box DNA to c‐MYC:MAX are mutually exclusive. [ABSTRACT FROM AUTHOR]

THO is a multi-protein complex involved in the formation of messenger ribonuclear particles (mRNPs) by coupling transcription with mRNA processing and export. THO is thought to be formed from five subunits, Tho2p, Hpr1p, Tex1p, Mft1p and Thp2p, and recent work has determined a low-resolution structure of the complex [Poulsen et al. (2014), PLoS One, 9, e103470]. A number of additional proteins are thought to be involved in the formation of mRNP in yeast, including Tho1, which has been shown to bind RNA in vitro and is recruited to actively transcribed chromatin in vivo in a THO-complex and RNA-dependent manner. Tho1 is known to contain a SAP domain at the N-terminus, but the ability to suppress the expression defects of the hpr1Δ mutant of THO was shown to reside in the RNA-binding C-terminal region. In this study, high-resolution structures of both the N-terminal DNA-binding SAP domain and C-terminal RNA-binding domain have been determined. [ABSTRACT FROM AUTHOR]