Identification of possible adenine nucleotide-binding sites in nitrogenase Fe- and MoFe-proteins by amino acid sequence comparison.

Published amino acid sequences for nitrogenase component polypeptides were compared with those of other proteins which also bind adenine nucleotides. Three sequences which might contribute to an adenine nucleotide-binding domain were found for the Fe-protein component of nitrogenase. The beta-subunit of the MoFe-protein (nifK gene product) contains a sequence which is similar to other proteins which exhibit ATPase activity. No similarities were observed for the alpha-subunit of this component. The findings are discussed in relation to the experimental data on adenine nucleotide binding and the proposed role of ATP in the enzyme mechanism.