A GENETIC REGION DOWNSTREAM OF THE HYDROGENASE STRUCTURAL GENES OF BRADYRHIZOBIUM-JAPONICUM THAT IS REQUIRED FOR HYDROGENASE PROCESSING

Deletion of a 2.9-kb chromosomal EcoRI fragment of DNA located 2.2 kb downstream from the end of the hydrogenase structural genes resulted in the complete loss of hydrogenase activity. The normal 65- and 35-kDa hydrogenase subunits were absent in the deletion mutants. Instead, two peptides of 66.5 and 41 kDa were identified in the mutants by use of anti-hydrogenase subunit-specific antibody. A hydrogenase structural gene mutant did not synthesize either the normal hydrogenase subunits or the larger peptides. Hydrogenase activity in the deletion mutants was complemented to near wild-type levels by plasmid PCF1, containing a 6.5-kb BglII fragment, and the 65- and 35-kDa hydrogenase subunits were also recovered in the mutants containing pCF1.