Protonation and deprotonation of the M, N, and O intermediates during the bacteriorhodopsin photocycle.
Protonation and deprotonation of the M, N, and O intermediates during the bacteriorhodopsin photocycle.
复制标题
细菌视紫红质光循环过程中 M、N 和 O 中间体的质子化和去质子化。
DOI：
10.1021/bi00481a015
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发表时间：
1990
期刊：
影响因子：
2.9
通讯作者：
Lanyi,JK
中科院分区：
文献类型：
--
作者：
Váró,G;Lanyi,JK
加州大学生理与生物物理系，加州尔湾92717摘要：用苯酚红和氯酚红在30^ s-50 ms时间范围内测量了细菌视紫红质（BR）在光驱动质子泵光循环过程中的瞬时pH变化。在pH为bbb70时，结果证实了先前的数据和建议，即在L-*·M反应中释放一个质子，并在n衰变过程中再次被吸收。这些可能是质子传输过程中的步骤。然而，在pH< 7时，时间分辨的pH痕迹是复杂的，表明有额外的质子化反应。该模型假设相对于BR， M和N的质子化态在-1到0之间变化，O的质子化态在0到+ 2之间变化。如果矢量质子转移过程的动力学与pH无关，则对数据的处理表明，一个pMa为5.9的残基在M和N中可质子化，两个pAla为6.5的残基在o中可协同质子化。检测到的额外质子不一定在矢量质子转移途径中（即它们可能是“玻尔质子”）。虽然它们必须反映br在通过N态和0态时的构象和/或邻近电离变化，但它们在输运中的作用（如果有的话）是不确定的。
Department of Physiology and Biophysics, University of California, Irvine, California 92717 Received January 22, 1990; Revised Manuscript Received April 24, 1990 abstract: Transient pH changes were measured with phenol red and chlorophenol red in the 30^ s-50-ms time range during the photocycle of bacteriorhodopsin (BR), the light-driven proton pump. At pH> 7, the results confirmed earlier data and suggestions that one proton is released during the L-*·M reaction, and taken up again during the decay of N. These are likely to be steps in the proton transport process. At pH< 7, however, the time-resolved pH traces were complex and indicated additional protonation reactions. The data were explained by a model which assumed pH-dependent protonation states for M and N which varied from-1 to 0, and for O which varied from 0 to+ 2, relative to BR. If the kinetics of the vectorial proton translocation process were taken as pH independent, this treatment of the data suggested that a residue with a pMa of 5.9 was made protonable in M and N and two residues with pAla’s of 6.5 were made cooperatively protonable in O. The additional protons detected are not necessarily in the vectorial proton transfer pathway (ie, they are probably “Bohr protons”), and while theymust reflect conformational and/or neighboring ionization changes in theBR as it passes through the, N, and 0 states, their role, if any, in the transport is uncertain.