McInnes C, Sönnichsen F D, Kay C M, Hodges R S, Sykes B D
Protein Engineering Network of Centres of Excellence and Synthetic Peptides Incorporated, University of Alberta, Edmonton, Canada.
Biochemistry. 1993 Dec 14;32(49):13432-40. doi: 10.1021/bi00212a008.
A synthetic peptide antigen corresponding to the C-terminus of Pseudomonas aeruginosa K strain pilin has been studied by one and two-dimensional NMR techniques. This peptide exists in two isomeric forms which arise as a result of the I138-P139 amide bond. An ensemble of solution conformations for the trans form of this 17-residue disulfide-bridged peptide (PAK 128-144) has been generated using a simulated annealing procedure in conjunction with distance and torsion angle restraints derived from NMR data. One major class of backbone conformations has been identified for this potential synthetic vaccine and indicates the presence of two beta-turns in the region 134-142. The region that has been established as the epitope for the monoclonal antibody PK99H is consistent with the region of the major conformers that exhibit the most definition in the ensemble (134-140) and also includes a type I beta-turn from residues 134 to 137. The generated structures are also consistent with observed NOEs characteristic of beta-turns and amide proton temperature coefficient data, which indicate the presence of two turns between residues 134 and 142. The presence of secondary structure within the epitope substantiates the theory that immunogenic regions of proteins are those which contain surface-exposed structural elements such as beta-turns. Further implications of the structure on antigenicity and cross-reactivity are discussed.
利用一维和二维核磁共振技术研究了一种与铜绿假单胞菌K菌株菌毛蛋白C末端相对应的合成肽抗原。由于I138 - P139酰胺键，该肽存在两种异构体形式。使用模拟退火程序结合从核磁共振数据得出的距离和扭转角限制条件，生成了这种17个残基的二硫键桥联肽（PAK 128 - 144）反式形式的溶液构象集合。已为这种潜在的合成疫苗确定了一类主要的主链构象，表明在134 - 142区域存在两个β-转角。已确定为单克隆抗体PK99H表位的区域与在构象集合中表现出最清晰定义的主要构象体区域（134 - 140）一致，并且还包括从残基134到137的I型β-转角。生成的结构也与观察到的β-转角特征性的核Overhauser效应（NOE）以及酰胺质子温度系数数据一致，这些数据表明在残基134和142之间存在两个转角。表位内二级结构的存在证实了蛋白质的免疫原性区域是那些包含表面暴露结构元件（如β-转角）的区域这一理论。还讨论了该结构对抗原性和交叉反应性的进一步影响。
