Conformations of isolated fragments of pancreatic polypeptide.
In spite of its short polypeptide chain, the pancreatic polypeptide molecule consists of a polyproline II type helix and alpha-helix. To understand the stability and formation of the alpha-helical region, we prepared some peptide fragments including the helical segment of chicken pancreatic polypeptide and studied their conformations by circular dichroism (CD). PP7-36 (a peptide fragment corresponding to residues 7-36 of chicken pancreatic polypeptide) showed a CD spectrum characteristic of the helix at pH 4.6 and at peptide concentrations as low as 1 microM. PP11-36 was able to form a helical conformation only at high peptide concentrations and not at concentrations lower than 10 microM. However, acetyl PP11-36 (in which the alpha-amino group is acetylated so that no positive charge exists at the N terminus) was able to form the helical conformation at pH 4.6 and at the peptide concentrations where PP11-36 could not. Succinyl PP12-36 (in which the alpha-amino group is succinylated to introduce a negative charge) was also able to form the helical conformation. The CD spectra of PP12-36 and PP13-36 were not characteristic of the helical conformation at all the pH values and peptide concentrations studied. Acetyl PP13-36, which has no charge at the N terminus, did not form the helix. On the other hand, succinyl PP13-36, which has a negative charge at the N-terminal end, did form the helix at pH 4.6. These findings indicate that the presence of the negative charge of carboxylate at the N-terminal region of a peptide fragment is important for helix formation.(ABSTRACT TRUNCATED AT 250 WORDS)
Tonan
K
K
Department of Biology, Faculty of Science, Osaka University, Japan.
Kawata
Y
Y
Hamaguchi
K
K
D000215:Acylation; D000595:Amino Acid Sequence; D000818:Animals; D002645:Chickens; D002851:Chromatography, High Pressure Liquid; D002942:Circular Dichroism; D008969:Molecular Sequence Data; D010191:Pancreatic Polypeptide; D010446:Peptide Fragments / Q000302:isolation & purification; D010455:Peptides / Q000138:chemical synthesis; D011487:Protein Conformation; D011489:Protein Denaturation; D013816:Thermodynamics
D010446:Peptide Fragments; D010455:Peptides; D010191:Pancreatic Polypeptide