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.