M. Dettin et al., A type-II beta-turn, proline-containing, cyclic pentapeptide as a buildingblock for the construction of models of the cleavage site of pro-oxytocin, J PEPT SCI, 7(7), 2001, pp. 358-373
Previous studies have indicated that proteolytic activation of pro-hormones
and pro-proteins occurs most frequently at the level of basic amino acids
arranged in doublets and that the dibasic sites are situated in or next to
beta -turns. investigations utilizing synthetic peptides reproducing the N-
terminal processing domain of pro-oxytocin-neurophysin have suggested a clo
se relationship between the secondary structure of the cleavage locus and e
nzyme recognition, the minimal recognized sequence being the -Pro-Leu-Gly-G
ly-Lys-Arg-Ala-Val-Leu- segment of the native precursor. NMR investigations
and energy minimization studies have demonstrated that this sequence is or
ganized in two type-II beta -turns involving the -Pro-Leu-Gly-Gly- and -Lys
-Arg-Ala-Val- sequences. To further strengthen the above reported hypothesi
s and to study the role of turn subtypes, a new proline containing cyclic s
ubstrate of the processing enzyme, in which the N-terminal side that comes
before the Lys-Arg pair is constrained to adopt a type-II beta -turn, has b
een synthesized. The presence of a type-II g-turn structure in this cyclic
peptide model has been demonstrated by a combined NMR, CD and FT-IR absorpt
ion investigation. A preliminary study shows that PC1 is able to recognize
and process our constrained substrate. Copyright (C) 2001 European Peptide
Society and John Wiley & Sons, Ltd.