McInnes C, Kay C M, Hodges R S, Sykes B D
Protein Engineering Network of Centres of Excellence and Synthetic Peptides Incorporated, Edmonton, Alberta, Canada.
Biopolymers. 1994 Sep;34(9):1221-30. doi: 10.1002/bip.360340910.
A 17-residue disulfide-bridged peptide (PAK 128-144) corresponding to the C-terminus of Pseudomonas aeruginosa pilin strain K has been studied by one- and two-dimensional nmr techniques. This synthetic immunogen has been found to exist as two distinct conformations in solution, which have been demonstrated to arise as a result of the isomerization of the I138-P139 amide bond. The two isomers occur in the ratio of 3:1 trans to cis at 5 degrees C. Sequential assignments for both forms have been accomplished through the use of nuclear Overhauser enhancement spectroscopy (NOESY) spectra and most side-chain resonances have been assigned using a combination of correlated spectroscopy, total correlated spectroscopy, and NOESY spectra. The presence of the cis isomer, which is considerably more predominant in the oxidized peptide, was confirmed by the observation of the characteristic NOEs between P139 and the preceding residue. Further corroboration was given by the disappearance of the cis resonances in the spectrum of the P139A analogue of PAK 128-144. From observation of the differences in the chemical shifts and amide proton temperature coefficients of the two isomers, it is apparent that the two forms differ markedly in their solution conformation. The biological implications of the isomerization are discussed.
通过一维和二维核磁共振技术研究了一种与铜绿假单胞菌菌毛蛋白菌株K的C端相对应的17个残基的二硫键连接肽（PAK 128 - 144）。已发现这种合成免疫原在溶液中以两种不同构象存在，这已被证明是由于I138 - P139酰胺键的异构化所致。在5摄氏度时，两种异构体以反式与顺式3:1的比例出现。通过使用核Overhauser增强光谱（NOESY）谱完成了两种形式的序列归属，并且大多数侧链共振通过相关光谱、全相关光谱和NOESY谱的组合进行了归属。通过观察P139与前一个残基之间的特征性核Overhauser效应（NOE），证实了顺式异构体的存在，其在氧化肽中更为主要。PAK 128 - 144的P139A类似物光谱中顺式共振的消失进一步证实了这一点。从观察两种异构体的化学位移和酰胺质子温度系数的差异可以明显看出，两种形式在溶液构象上有显著差异。讨论了异构化的生物学意义。
