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Abstract: Hydrothermal microbiotopes are characterized by the consumption and production of molecular hydrogen. Heterotrophic hyperthermophilic microorganisms (growth T opt⩾80°C) actively participate in the production of H2 in these environments through the fermentation of peptides and carbohydrates. Hyperthermophiles have been shown to approach the theoretical (Thauer) limit of 4mol of H2 produced per mole of glucose equivalent consumed, albeit at lower volumetric productivities than observed for mesophilic bacteria, especially enterics and clostridia. Potential advantages for biohydrogen production at elevated temperatures include fewer metabolic byproducts formed, absence of catabolic repression for growth on heterogeneous biomass substrates, and reduced loss of H2 through conversion to H2S and CH4 by mesophilic consortia containing sulfate reducers and methanogens. To fully exploit the use of these novel microorganisms and their constituent hydrogenases for biohydrogen production, development of versatile genetic systems and improvements in current understanding of electron flux from fermentable substrates to H2 in hyperthermophiles are needed. [Copyright &y& Elsevier]

Abstract: Key enzymes involved in end-product formation were identified in Thermoanaerobacterium saccharolyticum JW/SL-YS485, a thermophilic anaerobic bacterium under consideration as a biological catalyst for the conversion of cellulosic biomass to ethanol. Based on enzymatic assays and genome sequence analyses, pathways were identified that would lead to the generation of all major products from xylose fermentation: lactate, acetate, ethanol, hydrogen, and carbon dioxide. Pyruvate ferredoxin oxidoreductase is the primary pyruvate decarboxylating enzyme, producing carbon dioxide, reduced ferredoxin, and acetyl-CoA, and ferredoxin is likely oxidized by a specific hydrogenase. It is concluded that enzymes are present in this organism that could theoretically produce ethanol from carbohydrates at high yield. [Copyright &y& Elsevier]

Hydrogenases are enzymes found in all domains of life that catalyze a remarkably simple chemistry, the reversible oxidation of molecular hydrogen to protons and electrons. In order to perform this chemistry, cells have evolved, several different times, intricate organometal complexes built around a binuclear Ni-Fe or Fe-Fe center, with bound CO and CN− groups, as well as multiple FeS centers. These complicated enzymes have been an area of intense study for many decades, with interest peaking on the occasions of major increases in national energy costs. Interest in biologically generated hydrogen as a potential substitute for fossil fuels is again at the forefront, and the new tools of the postgenomic world available for manipulating these enzymes make it a truly viable possibility. Hydrogenases from hyperthermophilic microorganisms such as Pyrococcus furiosus and Thermotoga maritima, with optimal growth temperatures near 100°C, are of particular interest and promise for elucidating and manipulating these enzymatic mechanisms. [ABSTRACT FROM AUTHOR]

Presents a study which concluded that cytochrome cy of Rhodobacter capsulatus is attached to the cytoplasmis membrane by an uncleaved signal sequence-like anchor. Research methodology; Statistical information gathered from the study; Analysis of results obtained.

The D14C variant of Pyrococcus furiosus ferredoxin provides an extraordinary framework to investigate a [3Fe–4S] cluster at two oxidation levels and compare the results to its physiologic [4Fe–4S] counterpart in the very same protein. Our spectroscopic and computational study reveals vibrational property changes related to the electronic and structural aspects of both Fe–S clusters. [ABSTRACT FROM AUTHOR]

Nuclear inelastic scattering of 57Fe labeled [NiFe] hydrogenase is shown to give information on different states of the enzyme. It was thus possible to detect and assign FeCO and FeCN bending and stretching vibrations of the active site outside the spectral range of the FeS cluster normal modes. [ABSTRACT FROM AUTHOR]

Blick ins Zentrum: Die Methode der inelastischen kernresonanten Streuung (NRVS) wurde genutzt, um 57Fe ‐ markierte [NiFe] ‐ Hydrogenase in unterschiedlichen Zuständen des Enzyms zu untersuchen. Damit gelang es, die Fe ‐ CO ‐ und Fe ‐ CN ‐ Beuge ‐ und ‐ Streckschwingung außerhalb des Spektralbereichs der Normalmoden der Fe ‐ S ‐ Cluster zu detektieren und zuzuordnen (siehe Spektrum). [ABSTRACT FROM AUTHOR]

Abstract: We have used impulsive coherent vibrational spectroscopy (ICVS) to study the Fe(S-Cys)4 site in oxidized rubredoxin (Rd) from Pyrococcus furiosus (Pf). In this experiment, a 15fs visible laser pulse is used to coherently pump the sample to an excited electronic state, and a second <10fs pulse is used to probe the change in transmission as a function of the time delay. PfRd was observed to relax to the ground state by a single exponential decay with time constants of ∼255–275fs. Superimposed on this relaxation are oscillations caused by coherent excitation of vibrational modes in both excited and ground electronic states. Fourier transformation reveals the frequencies of these modes. The strongest ICV mode with 570nm excitation is the symmetric Fe–S stretching mode near 310cm−1, compared to 313cm−1 in the low temperature resonance Raman. If the rubredoxin is pumped at 520nm, a set of strong bands occurs between 20 and 110cm−1. Finally, there is a mode at ∼500cm−1 which is similar to features near 508cm−1 in blue Cu proteins that have been attributed to excited state vibrations. Normal mode analysis using 488 protein atoms and 558 waters gave calculated spectra that are in good agreement with previous nuclear resonance vibrational spectra (NRVS) results. The lowest frequency normal modes are identified as collective motions of the entire protein or large segments of polypeptide. Motion in these modes may affect the polar environment of the redox site and thus tune the electron transfer functions in rubredoxins. [Copyright &y& Elsevier]

Structural and functional characterization of the entire protein complement (the proteome) of an organism can provide an infrastructure upon which questions about biological pathways and systems biology can be framed. The technology necessary to perform this proteome-level structural and functional characterization is under development in numerous structural genomics and functional genomics initiatives. Given the ubiquity of metal active sites in a proteome, it seems appropriate to ask whether comprehensive local structural characterization of metal sites within a proteome (metalloproteomics) is either a valid or obtainable goal. With a proteome-wide knowledge of the active-site structures of all metalloproteins, one could start to ask how metal insertion, cluster assembly and metalloprotein expression are affected by growth conditions or developmental status etc. High-throughput X-ray absorption spectroscopy (HTXAS) is being developed as a technology for investigating the metalloproteome. In creating a pipeline from genome to metalloproteome, several bottlenecks to high-throughput determination of metal-site structures must be overcome. For example, automation of arraying small samples for XAS examination must be invented, automation of rapid data collection of multiple low-volume low-concentration samples must be developed, automation of data reduction and analysis must be perfected. Discussed here are the promises and the pitfalls of HTXAS development, including the results of initial feasibility experiments. [ABSTRACT FROM AUTHOR]

Rubredoxin from the hyperthermophilic archaeon Pyrococcus furiosus maintains its native structure at high temperatures (373 K). In order to investigate the role of hydrogen bonding, hydration and chain dynamics in this thermostability, wavelength-resolved Laue neutron diffraction data have been collected from the W3Y single mutant (Trp3→Tyr3) on the spallation neutron protein crystallography station (PCS) at Los Alamos Neutron Science Center. Data were measured at room temperature from nine crystal settings, each of approximately 12 h duration. The total data-measurement period was less than 5 d from a single crystal that had undergone H[sub2]/D[sub2]O exchange. The nominal resolution of the data is 2.1 Å. [ABSTRACT FROM AUTHOR]

The active site of [NiFe] hydrogenase is an excellent catalyst for hydrogen conversion with an intriguing ability to recover from exposure to dioxygen. In their Communication on page 724 ff., W. Lubitz, S. P. Cramer, and co‐workers use the synchrotron technique of nuclear resonance vibrational spectroscopy to identify normal modes associated with active‐site FeCN and FeCO motion. [ABSTRACT FROM AUTHOR]

Das aktive Zentrum der [NiFe] ‐ Hydrogenase ist ein exzellenter Katalysator der Wasserstoffumsetzung mit der faszinierenden Fähigkeit, sich nach Sauerstoffexposition zurückzubilden. W. Lubitz, S. P. Cramer et al. nutzen in ihrer Zuschrift auf S. 752 ff. die Synchrotrontechnik der kernresonanten inelastischen Streuung, um Normalmoden der Fe ‐ CN ‐ und Fe ‐ CO ‐ Bewegung im aktiven Zentrum zu identifizieren. [ABSTRACT FROM AUTHOR]

We report here the characterization of the first agmatine/cadaverine aminopropyl transferase (ACAPT), the enzyme responsible for polyamine biosynthesis from an archaeon. The gene PF0127 encoding ACAPT in the hyperthermophile Pyrococcus furiosus was cloned and expressed in Escherichia coli, and the recombinant protein was purified to homogeneity. P. furiosus ACAPT is a homodimer of 65 kDa. The broad substrate specificity of the enzyme toward the amine acceptors is unique, as agmatine, 1,3-diaminopropane, putrescine, cadaverine, and sym-nor-spermidine all serve as substrates. While maximal catalytic activity was observed with cadaverine, agmatine was the preferred substrate on the basis of the kcat/Km value. P. furiosus ACAPT is thermoactive and thermostable with an apparent melting temperature of 108°C that increases to 112°C in the presence of cadaverine. Limited proteolysis indicated that the only proteolytic cleavage site is localized in the C-terminal region and that the C-terminal peptide is not necessary for the integrity of the active site. The crystal structure of the enzyme determined to 1.8-Å resolution confirmed its dimeric nature and provided insight into the proteolytic analyses as well as into mechanisms of thermal stability. Analysis of the polyamine content of P. furiosus showed that spermidine, cadaverine, and sym-nor-spermidine are the major components, with small amounts of sym-nor-spermine and N-(3-aminopropyl)cadaverine (APC). This is the first report in Archaea of an unusual polyamine APC that is proposed to play a role in stress adaptation. [ABSTRACT FROM AUTHOR]