Hydrogenase

Chlamydomonas reinhardtii, a unicellular green alga, contains a hydrogenase enzyme, which is induced by anaerobic adaptation of the cells. Using the suppression subtractive hybridization (SSH) approach, the differential expression of genes under anaerobiosis was analyzed. A PCR fragment with similarity to the genes of bacterial Fe-hydrogenases was isolated and used to screen an anaerobic cDNA expression library of C. reinhardtii.

11p research12 01-06-2013 41 6   Download

Wolinella succinogenesgrows by oxidative phosphorylation with polysul®de as terminal electron acceptor and either H2 or formate as electron donor (polysul®de respiration). The function of the respiratory chains catalyzing these reactions was investigated. Proteoliposomes containing polysul®de reductase (Psr) and either hydrogenase or formate dehy-drogenase isolated fromthemembrane fraction ofWolinella succinogenescatalyzed polysul®de respiration, provided that methyl-menaquinone-6 isolated fromW. ...

10p research12 01-06-2013 33 4   Download

Hydrogenase and fumarate reductase isolated fromWoli-nella succinogeneswere incorporated into liposomes con-taining menaquinone. The two enzymes were found to be oriented solely to the outside of the resulting proteolipo-somes. The proteoliposomes catalyzed fumarate reduction by H2 which generated an electrical proton potential (Dwˆ 0.19 V, negative inside) in the same direction as that gen-erated by fumarate respiration in cells ofW. succinogenes.

10p research12 23-04-2013 41 2   Download

The purified membrane-bound [NiFe]-hydrogenase from Methanosarcina barkeriwas studied with electron para-magnetic resonance (EPR) focusing on the properties of the iron–sulphur clusters. TheEPRspectra showed signals from threedifferent [4Fe)4S] clusters.Twoof the clusters couldbe reduced under 101 kPa of H2, whereas the third cluster was only partially reduced.

11p tumor12 22-04-2013 36 3   Download

From the membrane fraction of the Gram-positive bacter-ium Carboxydothermus hydrogenoformans,anenzyme complex catalyzing the conversionofCOtoCO2andH2was purified. The enzyme complex showed maximal CO-oxidi-zing:H2 -evolving enzyme activity with 5% CO in the head-space (450 U per mg protein). Higher CO concentrations inhibited the hydrogenase present in the enzyme complex. For maximal activity, the enzyme complex had to be activated by either CO or strong reductants.

10p tumor12 22-04-2013 38 2   Download

Genes homologous to hydrogenase accessory genes are scattered over the whole genome in the cyanobacteriumSynechocystissp. PCC 6803. Deletion and insertion mutants of hypA1 (slr1675), hypB1 (sll1432), hypC, hypD, hypE and hypF were constructed and showed no hydrogenase activity. Involvement of the respective genes in maturation of the enzyme was con-firmed by complementation. Deletion of the additional homologueshypA2 (sll1078) and hypB2(sll1079) had no effect on hydrogenase activity. Thus, hypA1andhypB1are specific for hydrogenase maturation....

12p tumor12 20-04-2013 31 4   Download

We have isolated and characterized a second [Fe]-hydro-genasegene fromthegreenalga,Chlamydomonas reinhardtii. TheHydA2gene encodes a protein of 505 amino acids that is 74% similar and 68% identical to the known HydA1 hydrogenase fromC. reinhardtii.HydA2 contains all the conserved residues and motifs found in the catalytic core of the family of [Fe]-hydrogenases. We demonstrate that both theHydA1and theHydA2transcripts are expressed upon anaerobic induction, achieved either by neutral gas purging or by sulfur deprivation of the cultures. ...

9p fptmusic 16-04-2013 46 2   Download

There are at least two membrane-bound (HynSL and HupSL) and one soluble (HoxEFUYH) [NiFe]hydrogen-ases in Thiocapsa roseopersicinaBBS, a purple sulfur photosynthetic bacterium. Genes coding for accessory pro-teins that participate in the biosynthesis and maturation of hydrogenases seem to be scattered along the chromosome. Transposon-based mutagenesis was used to locate the hydrogenase accessory genes.

10p fptmusic 16-04-2013 33 3   Download

The expression of many membrane bound [NiFe] hydrogenases is regulated by their substrate molecule, hydrogen. The HupSL hydrogenase, encoded in the hupSLCDHIRoperon, probably plays a role in hydrogen recycling in the phototrophic purple bacterium, Thiocapsa roseopersicina BBS. RpoN, coding for sigma factor 54, was shown to be important for expres-sion, suggesting a regulated biosynthsis from the hup gene cluster.

10p fptmusic 12-04-2013 33 2   Download

Ech hydrogenase fromMethanosarcina barkeriis a member of a distinct group of membrane-bound [NiFe] hydrogenases with sequence similarity to energy-conserving NADH:quinone oxidoreductase (complex I). The sequence of the enzyme predicts the binding of three [4Fe-4S] clusters, one by subunit EchC and two by subunit EchF. Previous studies had shown that two of these clusters could be fully reduced under 10 5 Pa of H2at pH 7 giving rise to two distinct S½ electron paramagnetic resonance (EPR) signals, designated as the g¼1.89 and theg¼1.92 signal....

13p fptmusic 12-04-2013 36 2   Download

In the photosynthetic bacterium Rhodobacter capsulatus, the synthesis of the energy-producing hydrogenase, HupSL, is regulated by the substrate H2, which is detected by a regulatory hydrogenase, HupUV. The HupUV protein exhibits typical features of [NiFe] hydrogenases but, interestingly, is resistant to inactivation by O2. Understanding the O2 resistance of HupUV will help in the design of hydrogenases with high potential for bio-technological applications.

10p fptmusic 11-04-2013 30 1   Download

The hydrogenase maturation proteins HypF and HypE catalyze the synthesis of theCNligands of the active site iron of the NiFe-hydrogenases using carbamoylphosphate as a substrate. HypE protein fromEscherichia coliwas purified from a transformant overexpressing thehypEgene from a plasmid. PurifiedHypE in gel filtration experiments behaves predominantly as a monomer. It does not contain statisti-cally significant amounts ofmetals or of cofactors absorbing in the UV and visible light range.

0p awards 05-04-2013 47 2   Download

The soluble, cytoplasmic NAD + -reducing [NiFe]-hydro-genase fromRalstonia eutrophais aheterotetrameric enzyme (HoxFUYH) and contains two FMN groups. The purified oxidized enzyme is inactive in the H2-NAD + reaction, but can be activated by catalytic amounts of NADH. It was discovered that one of the FMN groups (FMN-a) is selec-tively released upon prolonged reduction of the enzyme with NADH. During this process, the enzyme maintained its tetrameric form, with one FMN group (FMN-b) firmly bound, but it lost its physiological activity – the reduction of NAD + by H2. ...

8p dell39 03-04-2013 37 5   Download

H2 -forming methylenetetrahydromethanopterin dehydro-genase (Hmd) is an unusual hydrogenase present in many methanogenic archaea. The homodimeric enzyme dubbed
metal-free hydrogenase does not contain iron–sulfur clus-ters or nickel and thus differs from [Ni-Fe] and [Fe-Fe] hydrogenases, which are all iron–sulfur proteins. Hmd preparations were found to contain up to 1 mol iron per 40 kDa subunit, but the iron was considered to be a con-taminant as none of the catalytic and spectroscopic pro-perties of the enzyme indicated that it was an essential component....

10p dell39 03-04-2013 52 4   Download

Considerable attention has been paid to the high cytotoxic potential of small, prefibrillar aggregates of proteins⁄peptides, either associated or not associated with amyloid diseases. Recently, we reported that different cell types are variously affected by early aggregates of the N-terminal domain of the prokaryotic hydrogenase maturation factor HypF (HypF-N), a pro-tein not involved in any disease.

17p inspiron33 26-03-2013 39 4   Download

In proteobacteria capable of H2oxidation under (micro)aerobic conditions, hydrogenase gene expression is often controlled in response to the availab-ility of H2. The H2 -sensing signal transduction pathway consists of a het-erodimeric regulatory [NiFe]-hydrogenase (RH), a histidine protein kinase and a response regulator.

12p inspiron33 23-03-2013 36 4   Download

Thiocapsa roseopersicinaBBS contains at least three different active NiFe hydrogenases: two membrane-bound enzymes and one apparently localized in the cytoplasm. In addition to the small and large structural subunits, additional proteins are usually associated with the NiFe hydrogenases, con-necting their activity to other redox processes in the cells.

11p vinaphone15 27-02-2013 32 2   Download

The sensitive to lysis D (SlyD) protein fromEscherichia coliis related to the FK506-binding protein family, and it harbours both peptidyl-prolyl cis–transisomerase (PPIase) and chaperone-like activity, preventing aggre-gation and promoting the correct folding of other proteins. Whereas a functional role of SlyD as a protein-folding catalyst in vivo remains unclear, SlyD has been shown to be an essential component for [Ni–Fe]-hydrogenase metallocentre assembly in bacteria.

16p vinaphone15 25-02-2013 27 4   Download

Methanosarcina mazeibelongs to the group of aceticlastic methanogens and converts acetate into the potent greenhouse gases CO2 and CH4. The aceticlastic respiratory chain involved in methane formation comprises the three transmembrane proteins Ech hydrogenase, F420 nonreducing hydroge-nase and heterodisulfide reductase.

8p viettel02 19-02-2013 40 2   Download

Cyanobacterial NAD(P) + -reducing reversible hydrogenases comprise five subunits. Four of them (HoxF, HoxU, HoxY, and HoxH) are also found in the well-described related enzyme from Ralstonia eutropha.

9p cosis54 09-12-2012 30 1   Download