Sieber V, Moe G R
Department of Chemistry and Biochemistry, University of Delaware, Newark 19716, USA.
Biochemistry. 1996 Jan 9;35(1):181-8. doi: 10.1021/bi950681o.
A 12 amino acid peptide, model BB, was designed to adopt a beta-hairpin tertiary structure in water that might be stabilized by a variety of local, nonlocal, polar, and nonpolar interactions. The conformational properties of model BB with and without an intramolecular disulfide bond (BB-O and BB-R, respectively) were characterized by NMR and CD spectroscopy. The set of observed short- and medium-range nOes were consistent with the formation of stable beta-hairpin-like structures by both BB-R and BB-O. BB-O adopts two distinct conformations that differ from each other in the designed reverse turn segment. A reasonably well-defined set of structures was obtained by using restraints from the NMR data in distance geometry calculations. None of the beta-hairpin-like structures contain a beta-sheet hydrogen bonding network. The distinctive feature of intrastrand and cross-strand pairing of threonine residues observed in all of the calculated structures suggests that hydrophobic interactions between the gamma-methyl groups of threonine residues may be the structure-determining interaction in model BB. The implications of these results for the formation of beta-sheets during protein folding, the aggregation of peptides as beta-sheets, and the de novo design of independently folding beta-hairpin-like peptides are considered.
设计了一种12个氨基酸的肽（模型BB），使其在水中呈现β-发夹三级结构，这种结构可能通过各种局部、非局部、极性和非极性相互作用得以稳定。分别通过核磁共振（NMR）和圆二色（CD）光谱对具有和不具有分子内二硫键的模型BB（分别为BB-O和BB-R）的构象性质进行了表征。观察到的短程和中程核Overhauser效应（nOes）与BB-R和BB-O均形成稳定的β-发夹样结构一致。BB-O呈现出两种不同的构象，它们在设计的反向转角片段中彼此不同。通过在距离几何计算中使用来自NMR数据的约束条件，获得了一组定义合理的结构。所有β-发夹样结构均不包含β-折叠氢键网络。在所有计算结构中观察到的苏氨酸残基链内和链间配对的独特特征表明，苏氨酸残基γ-甲基之间的疏水相互作用可能是模型BB中的结构决定性相互作用。考虑了这些结果对蛋白质折叠过程中β-折叠的形成、肽作为β-折叠的聚集以及独立折叠的β-发夹样肽的从头设计的影响。
