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
