N.m.r. and computer-simulated conformational analyses of a nonapeptide found in a human salivary proline-rich glycoprotein.
The amino acid sequence G(1)-P(2)-P(3)-P(4)-H(5)-P(6)-G(7)-K(8)-P(9) occurs twice in the proline-rich glycoprotein (PRG) found in human parotid saliva. As part of our efforts to elucidate the structure-function relationships of PRG, this nonapeptide sequence (PRG9) was synthesized for the purpose of conformational analyses by high-resolution proton n.m.r. spectroscopy and computer-modeling. The empirical n.m.r. spectrum differed from the simulated spectrum in that the overall chemical shift locations were displaced from their random coil positions and the five proline residues had non-degenerate C alpha H alpha protons. Other n.m.r. data indicated that no intramolecular hydrogen-bonding was present in the PRG. In conjunction with X-ray crystallographic data on a triproline-containing model compound (Kartha, g., Ashida, T. & Kakudo, M. (1974) Acta Cryst. B30, 1861-1866), four energy-minimized PRG9 structures were obtained. Two of the structures were energetically unfavorable, while the other two conformations were reasonable. The two most likely structures gave all prolines an S-type ring pucker, the P(2)-P(3)-P(4) sequence as a poly-L-proline II helix, the H(5) phi = -90.3 degrees, P(6) and P(9) with trans peptide bond orientation, G(7) in an extended state, and the K(8) phi = -93.2 degrees or -146.8 degrees for structures #1 and #2, respectively.
Loomis
R E
RE
State University of New York, School of Dental Medicine, Buffalo.
Tseng
C C
CC
Bergey
E J
EJ
Levine
M J
MJ
D003198:Computer Simulation; D006801:Humans; D007202:Indicators and Reagents; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008958:Models, Molecular; D009842:Oligopeptides / Q000138:chemical synthesis; D010455:Peptides / Q000138:chemical synthesis; D055232:Proline-Rich Protein Domains; D011487:Protein Conformation; D012471:Salivary Proteins and Peptides
D007202:Indicators and Reagents; D009842:Oligopeptides; D010455:Peptides; D012471:Salivary Proteins and Peptides