Disease relevance of hycG

• Hydrogenase activity in E. coli requires the NikABCDE nickel transporter, which is transcriptionally repressed by NikR in the presence of excess nickel [1].
• It is now clear that the genes controlling [NiFe] hydrogenase activity in many bacteria including Azotobacter chroococcum, Alcaligenes eutrophus, Rhizobium leguminosarum, Rhodobacter capsulatus and Escherichia coli are highly conserved, organized in much the same manner, and likely derived from a common ancestor [2].
• A gene bank of the 450-kilobase (kb) megaplasmid pHG1 from the hydrogen-oxidizing bacterium Alcaligenes eutrophus H16 was constructed in the broad-host-range mobilizable vector pSUP202 and maintained in Escherichia coli. hox DNA was identified by screening the E. coli gene bank for restoration of hydrogenase activity in A. eutrophus Hox mutants [3].
• Regulation of hydrogenase activity in enterobacteria [4].
• Regulation of hydrogenase activity in vegetative cells of Anabaena variabilis [5].

High impact information on hycG

• The wild-type himA gene, cloned in plasmid pBO2, was introduced into the IR4 strain and shown to restore, in trans, hydrogenase activity and autotrophic growth in the mutant [6].
• Both heterotrophically growing cells and cells induced to express hydrogenase activity contain a protein that specifically binds to the hup promoter region [7].
• The two selected mutants, BCX1 and BCX2, which contained the kanamycin-resistance gene in opposite orientation, still exhibited hydrogenase activity when assayed with the artificial electron acceptors benzylviologen and methylene blue [8].
• The hydrogenase activity of fnr strains can be restored by the presence of a functional hydC gene on a multicopy plasmid [9].
• An E. coli hypE mutant, with no hydrogenase activity, was also impaired in NR-mediated iron reduction activity [10].

Chemical compound and disease context of hycG

• Proteus vulgaris, Escherichia coli, and Citrobacter freundii cells were devoid of hydrogenase activity when grown on complex medium or minimal medium plus glucose in the presence of saturating levels of dissolved oxygen [4].
• A mutant strain of Escherichia coli, strain AK23, is devoid of hydrogenase activity when grown anaerobically on glucose and cannot grow on H2 plus fumarate [11].

Biological context of hycG

• Reciprocally, an E. coli strain harboring a deleted nik operon recovered hydrogenase activity by heterologous complementation with the B. suis nik locus [12].
• Here we show that cosmid pAL618 contains all of the genetic information required to confer high levels of hydrogenase activity on the naturally Hup- strains R. leguminosarum UML2 and Rhizobium phaseoli CFN42, and we also describe in detail the organization of hup genes on pAL618 [13].
• By means of Tn5-mediated insertional mutagenesis, a class of mutants was isolated (class I) that had retained 20% of the overall hydrogenase activity [14].
• Cell growth was inhibited by CO, and the cells grew but lacked hydrogenase activity when grown in the presence of nitrate [4].
• The activities of plasmid-determined beta-galactosidase and chromosome-encoded hydrogenase changed in parallel in response to various growth conditions (light or dark, aerobiosis or anaerobiosis, and presence or absence of ammonia or of H2), showing that changes in hydrogenase activity were due to changes in enzyme synthesis [15].

Anatomical context of hycG

• The enzyme constituted about 8% of the hydrogenase activity found in the detergent-dispersed membranes, the remainder being attributable to hydrogenase isoenzyme 2 [16].

Associations of hycG with chemical compounds

• Class I mutants produced hydrogenase activity (determined by using a tritium-exchange assay) and formate hydrogenlyase activity but lacked the ability to reduce benzyl viologen or fumarate with H2 as the electron donor [17].
• Cells grown anaerobically in the presence of CO (an inhibitor of hydrogenase) or nitrate (an electron acceptor) lacked hydrogenase activity [4].
• However, hydrogenase activity in the heterocysts was insensitive to both light (greater than 5,000 lx) and O2 (10%) [5].
• Redox control of hydrogenase activity in the green alga Scenedesmus obliquus by thioredoxin and other thiols [18].
• Sucrose-gradient centrifugation separated hydrogenase activity into two peaks, the less dense of which was phospholipid-associated and turbid, thereby showing successful incorporation [19].

Other interactions of hycG

• Mutations in the fhlA gene also abolished production of the hydrogenase activity associated with formate hydrogenlyase activity [20].

References