Gooley P R, MacKenzie N E
Dept. of Pharmaceutical Sciences, College of Pharmacy, University of Arizona, Tucson 85721.
FEBS Lett. 1990 Jan 29;260(2):225-8. doi: 10.1016/0014-5793(90)80109-v.
Comparative analysis of nuclear Overhauser effects show that the time average conformation of the wild-type and mutant Pro----Ala-35 Rhodobacter capsulatus cytochrome c2 are indistinguishable. The ring resonances of Phe-51 and Tyr-53 show that their ring flip rates increase in P35A. NH proton exchange studies show that the exchange rates of the NH of Gly-34 and the NpiH of His-17 increase by approximately 10(2) in P35A suggesting that their respective hydrogen bonds are destabilized in this protein. However, 3JchiNH 1H and 15N chemical shift data argue that these bonds are intact. These data are compatible if the replacement of a Pro with an Ala residue forms a cavity or increases local flexibility thus reducing steric hinderance and increasing solvent accessibility.
核Overhauser效应的比较分析表明，野生型和突变型（Pro35Ala）荚膜红细菌细胞色素c2的时间平均构象无法区分。苯丙氨酸-51和酪氨酸-53的环共振表明，在P35A中它们的环翻转速率增加。NH质子交换研究表明，在P35A中，甘氨酸-34的NH和组氨酸-17的NpiH的交换速率增加了约10²，这表明它们各自的氢键在该蛋白质中不稳定。然而，3JχNH ¹H和¹⁵N化学位移数据表明这些键是完整的。如果用丙氨酸残基取代脯氨酸会形成一个空腔或增加局部柔韧性，从而减少空间位阻并增加溶剂可及性，那么这些数据是相符的。
