Identification of Genes Involved in Fe-S Cluster Biosynthesis of Nitrogenase in WLY78.

NifS and NifU (encoded by and ) are generally dedicated to biogenesis of the nitrogenase Fe-S cluster in diazotrophs. However, and are not found in N-fixing strains, and the mechanisms involved in Fe-S cluster biosynthesis of nitrogenase is not clear. Here, we found that the genome of WLY78 contains the complete operon, a partial operon, a -like gene, two -like genes (-like and ), and two genes. Deletion and complementation studies showed that the , and genes of the operon, and -like and genes were involved in the Fe-S cluster biosynthesis of nitrogenase. Heterologous complementation studies demonstrated that the -like gene of WLY78 is interchangeable with , but WLY78 SufCDB cannot be functionally replaced by NifU. In addition, and are able to complement the WLY78 mutant. Our findings thus indicate that the NifS-like and SufCDB proteins are the specific sulfur donor and the molecular scaffold, respectively, for the Fe-S cluster formation of nitrogenase in WLY78. YutI can be an Fe-S cluster carrier involved in nitrogenase maturation in WLY78.