Loomis R E, Gonzalez M, Loomis P M
State University of New York, School of Dental Medicine, Department of Oral Biology, Buffalo.
Int J Pept Protein Res. 1991 Nov;38(5):428-39. doi: 10.1111/j.1399-3011.1991.tb01523.x.
The solution-state conformations of eight proline-containing peptide fragments found in human salivary proline-rich glycoprotein (PRG) were investigated in 2 x distilled water (treated with metal ion chelating resin) using 13C-nuclear magnetic resonance (NMR) and circular dichroism (CD) spectroscopy. The peptide sequences and acronyms were as follows: PRG9-2 = NH2-G(1)-P(2)-CONH2, PRG9-3 = NH2-G(1)P(2)-P(3)-CONH2, PRG9-4 = NH2-G(1)-P(2)-P(3)-P(4)-CONH2, PRG9-5 = NH2-G(1)-P(2)-P(3)-P(4)-H(5)-CONH2, PRG9-6 = NH2-G(1)-P(2)-P(3)-P(4)-H(5)-P(6)-CONH2, PRG9-7 = NH2-G(1)-P(2)-P(3)-P(4)-H(5)-P(6)-G(7)-CONH2, PRG9-8 = NH2-G(1)-P(2)-P(3)-P(4)-H(5)-P(6)-G(7)-K(8)-CONH2 and PRG9-9 = NH2-G(1)-P(2)-P(3)-P(4)-H(5)-P(6)-G(7)-K(8)-P(9)-CONH2. Sequence-specific resonance assignments from the 13C-NMR spectra indicated that the trans proline isomer dominated the conformations of the peptides. CD results clearly showed the presence of the poly-L-proline II helix as the major conformation in PRG9-3----PRG9-5, supplemented by beta- and/or gamma-turns in PRG9-6----PRG9-9. These data suggest that in "metal free" water, native PRG could contain several small poly-L-proline II helices along with beta- and/or gamma-turns. Since proline is the major amino acid present in native PRG, these localized conformations may contribute to PRG's global conformation and act as a primary force in determining its biological activities.
利用13C核磁共振（NMR）和圆二色性（CD）光谱，研究了在人唾液富含脯氨酸糖蛋白（PRG）中发现的8个含脯氨酸肽片段在2倍蒸馏水（用金属离子螯合树脂处理）中的溶液态构象。肽序列和缩写如下：PRG9 - 2 = NH2 - G(1)-P(2)-CONH2，PRG9 - 3 = NH2 - G(1)P(2)-P(3)-CONH2，PRG9 - 4 = NH2 - G(1)-P(2)-P(3)-P(4)-CONH2，PRG9 - 5 = NH2 - G(1)-P(2)-P(3)-P(4)-H(5)-CONH2，PRG9 - 6 = NH2 - G(1)-P(2)-P(3)-P(4)-H(5)-P(6)-CONH2，PRG9 - 7 = NH2 - G(1)-P(2)-P(3)-P(4)-H(5)-P(6)-G(7)-CONH2，PRG9 - 8 = NH2 - G(1)-P(2)-P(3)-P(4)-H(5)-P(6)-G(7)-K(8)-CONH2以及PRG9 - 9 = NH2 - G(1)-P(2)-P(3)-P(4)-H(5)-P(6)-G(7)-K(8)-P(9)-CONH2。13C - NMR光谱的序列特异性共振归属表明，反式脯氨酸异构体主导了肽的构象。CD结果清楚地表明，聚-L-脯氨酸II螺旋是PRG9 - 3至PRG9 - 5中的主要构象，PRG9 - 6至PRG9 - 9中还存在β-和/或γ-转角作为补充。这些数据表明，在“无金属”水中，天然PRG可能包含几个小的聚-L-脯氨酸II螺旋以及β-和/或γ-转角。由于脯氨酸是天然PRG中存在的主要氨基酸，这些局部构象可能有助于PRG的整体构象，并在决定其生物活性方面起主要作用。
