Localization of the retinal protonated Schiff base counterion in rhodopsin.
Localization of the retinal protonated Schiff base counterion in rhodopsin.
复制标题
视紫红质中视网膜质子化席夫碱抗衡离子的定位。
DOI：
10.1016/s0006-3495(93)81117-2
复制
发表时间：
1993
影响因子：
3.4
通讯作者：
Smith,SO
中科院分区：
文献类型：
--
作者：
Han,M;DeDecker,BS;Smith,SO
半经验分子轨道计算与~（13）C NMR化学位移相结合，定位了脊椎动物视紫红质视网膜结合位点的反式异构体。计算了11-顺式-视黄基质子化席夫碱的沿着多烯链的电荷密度（11-cis-RPSB）发色团，其具有1）在距席夫碱氮的不同距离处的氯离子抗衡离子，2）在沿着C10至C15的视黄醛链的不同位置处和在席夫碱氮处的一个或两个氯离子抗衡离子，（3）C12附近视网膜平面外的羧酸根计数器。与11-cis-RPSB氯化物模型化合物相比，增加与席夫碱的负电荷的距离导致偶数和奇数碳上交替的负和正部分电荷的增强。相反，视紫红质的观察到的13 C NMR数据显示出相对于11-顺式-RPSB.Cl从C8到C13的低场化学位移，对应于在这些位置部分正电荷的净增加或部分负电荷的净减少（Smith，S. O.，I. Palings，M. E.作者声明：H. de Groot，J. Lugtenburg，R. A. Mathies和R. G.格里芬1990.生物化学。29：8158-8164）。在视紫红质NMR化学位移中反映的电荷密度的异常变化可以通过在C12上方放置单个负电荷来定性地建模。当使用羧酸根离子来模拟视网膜结合位点时，计算的拟合得到改善。在模型中包含水不会改变NMR数据的拟合，尽管它与基于其他方法的观察结果一致。（250字处删节）
Semiempirical molecular orbital calculations are combined with 13C NMR chemical shifts to localize the counterion in the retinal binding site of vertebrate rhodopsin. Charge densities along the polyene chain are calculated for an 11-cis-retinylidene protonated Schiff base (11-cis-RPSB) chromophore with 1) a chloride counterion at various distances from the Schiff base nitrogen, 2) one or two chloride counterions at different positions along the retinal chain from C10 to C15 and at the Schiff base nitrogen, and 3) a carboxylate counterion out of the retinal plane near C12. Increasing the distance of the negative counterion from the Schiff base results in an enhancement of alternating negative and positive partial charge on the even- and odd-numbered carbons, respectively, when compared to the 11-cis-RPSB chloride model compound. In contrast, the observed 13C NMR data of rhodopsin exhibit downfield chemical shifts from C8 to C13 relative to the 11-cis-RPSB.Cl corresponding to a net increase of partial positive or decrease of partial negative charge at these positions (Smith, S. O., I. Palings, M. E. Miley, J. Courtin, H. de Groot, J. Lugtenburg, R. A. Mathies, and R. G. Griffin. 1990. Biochemistry. 29:8158–8164). The anomalous changes in charge density reflected in the rhodopsin NMR chemical shifts can be qualitatively modeled by placing a single negative charge above C12. The calculated fit improves when a carboxylate counterion is used to model the retinal binding site. Inclusion of water in the model does not alter the fit to the NMR data, although it is consistent with observations based on other methods.(ABSTRACT TRUNCATED AT 250 WORDS)