Abstract
Bj488, an up-regulated gene in Bradyrhizobium japonicum bacteroid from nodules at 28 days after infection, was investigated. It displayed a conserved gene homologue to COX17, sharing a potential metal binding motif H(M)X10MX21HXM. COX17 is one of the metallochaperones which conserved in the yeast and human proteins, consistent with a role as a shuttle protein for delivering copper to mitochondria. Metallochaperones are necessary in copper ion delivery and insertion for the assembly of cytochrome c oxidase. The Bj488 mutant resulted in defective symbiotic nitrogen fixation and showed the Fix- phenotype. The significant decrease of Cytochrome c oxidase activity was observed in a Bj488 bacteroids under microaerobic condition, whereas the activity was comparable in cells grown aerobically in free-living cell. It is suggested that Bj488 protein is proposed to have an important role in copper ion delivery to cytochrome c oxidase, which might be induced at low oxygen concentrations.
