hydA and hydB, the genes encoding the large (46-kDa) and small (13. 5-kDa) subunits of the periplasmic [Fe] hydrogenase from Desulfovibrio desulfuricans ATCC 7757, have been cloned and sequenced. The deduced amino acid sequence of the genes product showed complete identity to the sequence of the well-characterized [Fe] hydrogenase from the closely related species Desulfovibrio vulgaris Hildenborough (G. Voordouw and S. Brenner, Eur. J. Biochem. 148:515-520, 1985). The data show that in addition to the well-known signal peptide preceding the NH2 terminus of the mature small subunit, the large subunit undergoes a carboxy-terminal processing involving the cleavage of a peptide of 24 residues, in agreement with the recently reported data on the three-dimensional structure of the enzyme (Y. Nicolet, C. Piras, P. Legrand, E. C. Hatchikian, and J. C. Fontecilla-Camps, Structure 7:13-23, 1999). We suggest that this C-terminal processing is involved in the export of the protein to the periplasm.