CARBOXY-TERMINAL PROCESSING OF THE LARGE SUBUNIT OF [NIFE] HYDROGENASES

Two electrophoretic forms of the large subunit of the soluble periplas mic [NiFe] hydrogenase from Desulfovibrio gigas have been detected by Western analysis. The faster moving form co-migrates with the large su bunit from purified, active enzyme. Amino acid sequence and compositio n of the C-terminal tryptic peptide of the large subunit from purified hydrogenase revealed that it is 15 amino acids shorter than that pred icted by the nucleotide sequence. Processing of the nascent large subu nit occurs by C-terminal cleavage between His536 and Val537, residues which are highly conserved among [NiFe] hydrogenases. Mutagenesis of t he analogous residues, His582 and Val583, in the E. coli hydrogenase-1 (HYD1) large subunit resulted in significant decrease in processing a nd HYD1 activity.