Correspondence of the Larger Subunit of the MoFe-Protein in Clostridial Nitrogenase to the nif D Gene Products of Other N2-Fixing Organisms1

Abstract

The amino(N)-terminal sequence of the larger subunit (α) of the MoFe-protein from Clostridium pasteurianum was determined up to 179 amino acid residues by analyses of BrCN and tryptic peptides of the original subunit. Apparent similarities exist among the sequence of the clostridial α-subunit, that of the smaller subunit (β) of the Azotobacter vinelandii MoFe-protein, and those predicted from the nucleotide sequences of nif D genes in Klebsiella pneumoniae and Anabaena 7120. In comparing the sequences of C. pasteurianum and K. pneumoniae, 45% of residues are identical of a total of 184 sites. Therefore, the larger subunit of the clostridial MoFe-protein must correspond to the nif D gene product of K. pneumoniae.