Biochemical pathway for the biosynthesis of the Cu center in bacterial cytochrome c oxidase.

The di-copper center Cu is an essential metal cofactor in cytochrome oxidase (Cox) of mitochondria and many prokaryotes, mediating one-electron transfer from cytochrome c to the site for oxygen reduction. Cu is located in subunit II (CoxB) of Cox and protrudes into the periplasm of Gram-negative bacteria or the mitochondrial intermembrane space. How the two copper ions are brought together to build CoxB·Cu is the subject of this review.

Structural basis and mechanism for metallochaperone-assisted assembly of the Cu center in cytochrome oxidase.

The mechanisms underlying the biogenesis of the structurally unique, binuclear Cu•Cu redox center (Cu) on subunit II (CoxB) of cytochrome oxidases have been a long-standing mystery. Here, we reconstituted the CoxB•Cu center in vitro from -CoxB and the -forms of the copper transfer chaperones ScoI and PcuC. A previously unknown, highly stable ScoI•Cu•CoxB complex was shown to be rapidly formed as the first intermediate in the pathway.

Requirements for Efficient Thiosulfate Oxidation in Bradyrhizobium diazoefficiens.

One of the many disparate lifestyles of is chemolithotrophic growth with thiosulfate as an electron donor for respiration. The employed carbon source may be CO₂ (autotrophy) or an organic compound such as succinate (mixotrophy). Here, we discovered three new facets of this capacity: (i) When thiosulfate and succinate were consumed concomitantly in conditions of mixotrophy, even a high molar excess of succinate did not exert efficient catabolite repression over the use of thiosulfate.

How periplasmic thioredoxin TlpA reduces bacterial copper chaperone ScoI and cytochrome oxidase subunit II (CoxB) prior to metallation.

Two critical cysteine residues in the copper-A site (Cu(A)) on subunit II (CoxB) of bacterial cytochrome c oxidase lie on the periplasmic side of the cytoplasmic membrane. As the periplasm is an oxidizing environment as compared with the reducing cytoplasm, the prediction was that a disulfide bond formed between these cysteines must be eliminated by reduction prior to copper insertion. We show here that a periplasmic thioredoxin (TlpA) acts as a specific reductant not only for the Cu(2+) transfer chaperone ScoI but also for CoxB.

A link between arabinose utilization and oxalotrophy in Bradyrhizobium japonicum.

Rhizobia have a versatile catabolism that allows them to compete successfully with other microorganisms for nutrients in the soil and in the rhizosphere of their respective host plants. In this study, Bradyrhizobium japonicum USDA 110 was found to be able to utilize oxalate as the sole carbon source. A proteome analysis of cells grown in minimal medium containing arabinose suggested that oxalate oxidation extends the arabinose degradation branch via glycolaldehyde.