Sequence of the nifD Gene Coding for the α Subunit of Dinitrogenase from the Cyanobacterium Anabaena
Abstract
The nucleotide sequence of nifD, the structural gene for the α subunit of dinitrogenase from Anabaena 7120, has been determined. The coding sequence contains 1,440 nucleotides, which predict an amino acid sequence of 480 residues and Mr of 54,283. The predicted sequence contains eight cysteines, of which five are conserved with respect to adjoining sequences and position relative to the α subunits of dinitrogenase from Azotobacter, Clostridium, and Klebsiella. Because there are also five conserved cysteines in the β subunit of Anabaena dinitrogenase [Mazur, B. J. & Chiu, C.-F. (1982) Proc. Natl. Acad. Sci. USA 79, 6782-6786], the number of cysteine residues participating as ligands to FeS clusters is likely to be 20 per α2β2 tetramer. This number is sufficient to accommodate the known four Fe4S4 clusters, leaving at least four cysteines to be shared among the two FeMo cofactors and the more poorly characterized two-iron center. Although the α- and β-subunit gene sequences are not recognizably homologous, their secondary structures, predicted from the sequences, indicate similar domains around three of the conserved cysteine residues.
- Publication:
-
Proceedings of the National Academy of Science
- Pub Date:
- August 1983
- DOI:
- 10.1073/pnas.80.15.4723
- Bibcode:
- 1983PNAS...80.4723L