Zhang Y N, el-Sayed M A, Stern L J, Marti T, Mogi T, Khorana H G
Department of Chemistry and Biochemistry, University of California, Los Angeles 90024.
Photochem Photobiol. 1993 Jun;57(6):1027-31. doi: 10.1111/j.1751-1097.1993.tb02966.x.
Membrane-buried proline residues are found in many transport proteins. To study their roles in the structure and function of bacteriorhodopsin (bR), effects of the individual substitutions of Pro-50, Pro-91 and Pro-186 on the deprotonation and reprotonation kinetics of the Schiff base (SB) were determined by flash photolysis. The obtained rate constants and the amplitudes of the slow and fast components were compared with those of ebR (wild-type bR, the native protein that is expressed in Escherichia coli). The deprotonation rates of PSB were found to be 10 times faster than that of ebR for P50A, P91A and P91G mutants, and 4 times faster for the P50G mutant. These mutations also increased the initial reprotonation rate of the SB, although the overall change in the reprotonation rate is not as significant as that in the deprotonation rate. Our results indicate that Pro-50 and Pro-91, as well as Pro-186, are important for the proton-pumping function of bR.
膜埋脯氨酸残基存在于许多转运蛋白中。为了研究它们在细菌视紫红质（bR）的结构和功能中的作用，通过闪光光解测定了Pro-50、Pro-91和Pro-186的单个取代对席夫碱（SB）去质子化和再质子化动力学的影响。将得到的速率常数以及慢成分和快成分的幅度与ebR（野生型bR，在大肠杆菌中表达的天然蛋白）的进行比较。发现对于P50A、P91A和P91G突变体，PSB的去质子化速率比ebR快10倍，对于P50G突变体快4倍。这些突变也增加了SB的初始再质子化速率，尽管再质子化速率的总体变化不如去质子化速率那么显著。我们的结果表明，Pro-50和Pro-91以及Pro-186对bR的质子泵功能很重要。
