A type-II beta-turn, proline-containing, cyclic pentapeptide as a building block for the construction of models of the cleavage site of pro-oxytocin.
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 close relationship between the secondary structure of the cleavage locus and enzyme recognition, the minimal recognized sequence being the -Pro-Leu-Gly-Gly-Lys-Arg-Ala-Val-Leu- segment of the native precursor. NMR investigations and energy minimization studies have demonstrated that this sequence is organized in two type-II beta-turns involving the -Pro-Leu-Gly-Gly- and -Lys-Arg-Ala-Val- sequences. To further strengthen the above reported hypothesis and to study the role of turn subtypes, a new proline containing cyclic substrate of the processing enzyme, in which the N-terminal side that comes before the Lys-Arg pair is constrained to adopt a type-lI beta-turn, has been synthesized. The presence of a type-II beta-turn structure in this cyclic peptide model has been demonstrated by a combined NMR, CD and FT-IR absorption investigation. A preliminary study shows that PC1 is able to recognize and process our constrained substrate.
Dettin
M
M
Department of Chemical Process Engineering, University of Padova, Italy.
Falcigno
L
L
Campanile
T
T
Scarinci
C
C
D'Auria
G
G
Cusin
M
M
Paolillo
L
L
Di Bello
C
C
D016282:Aspartic Acid Endopeptidases / Q000737:chemistry; D002942:Circular Dichroism; D006868:Hydrolysis; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008956:Models, Chemical; D008968:Molecular Conformation; D009842:Oligopeptides / Q000138:chemical synthesis* / Q000737:chemistry; D010121:Oxytocin / Q000031:analogs & derivatives* / Q000737:chemistry*; D010456:Peptides, Cyclic / Q000138:chemical synthesis* / Q000737:chemistry; D011392:Proline / Q000737:chemistry; D043484:Proprotein Convertases; D017550:Spectroscopy, Fourier Transform Infrared / Q000379:methods
D009842:Oligopeptides; D010456:Peptides, Cyclic; D010121:Oxytocin; C046278:oxytocin, Gly-Lys-Arg-; D011392:Proline; D043484:Proprotein Convertases; D016282:Aspartic Acid Endopeptidases