Catalytic cysteine residues of ER-60 protease

ER-60 protease contains two CGHC motifs that appear to include an active si te cysteine residue(s). Its proteolytic activity was lost with a double mut ation of the C-terminal cysteines of the two motifs to alanine, but not wit h a single mutation of the C-terminal cysteine of either of the motifs to a lanine, This suggests that these C-terminal cysteines independently constit ute the catalytic active site. A mutation of both histidine residues in the two CGHC motifs to serine did not abolish the proteolytic activity, sugges ting these histidine residues in the CGHC motifs do not constitute the cata lytic dyed of ER-60 protease, (C) 2000 Federation of European Biochemical S ocieties.