ACTIVE-SITE PEPTIDES WITH CXXC-MOTIF ON MAP-RESIN CAN MIMIC PROTEIN DISULFIDE-ISOMERASE ACTIVITY

Two conserved Trp-Cys-Gly-His-Cys (WCGHC) sequences are assigned to ac t as catalytic sites for protein disulfide isomerase. Peptides contain ing the active site sequence, Ala-Pro-Trp-Cys-Gly His-Cys-Lys(APWCGHCK ), were synthesized both in a mono-molecular form and on multiple anti gen peptide (MAP) resin or Wang resin by the 9-fluoroenylmethoxy-carbo nyl (Fmoc)-based solid-phase method. With scrambled RNase as a substra te, the (APWCGHCK)8-MAP was first shown to mimic the PDI activity,whic h was one thousandth of that of bovine PDI and comparable to that of t hioredoxin. APWCGPCK and APWCGHCK, however, did not display a disulfid e isomerase activity even at a concentration 8 times higher than that of (APWCGHCK)8-MAP. It was assumed that a sterically proper proximity of at least two active site peptides with CXXC motif was required for the expression of PDI activity. (C) 1995 Academic Press, Inc.