Katre N V, Wolber P K, Stoeckenius W, Stroud R M
Proc Natl Acad Sci U S A. 1981 Jul;78(7):4068-72. doi: 10.1073/pnas.78.7.4068.
After chemical reduction of the retinylidene-lysine Schiff base linkage in bacteriorhodopsin, the retinyl residue is covalently attached to Lys-216 (with a possible minor fraction on Lys-172) or to both Lys-216(172) and Lys-40/41. The linkage site (up to 100% on Lys-216; up to 70% on Lys-40/41) depends on whether the sample is reduced in the light or dark, whether the sample is light or dark adapted, and on temperature. Absorbance and circular dichroism spectra indicate that the retinyl residue is in its original binding site after reduction in the light. Thus, the different attachment sites may reflect changes that occur during the photoreaction cycle or during light/dark adaptation, or the reduction of accidental physiologically irrelevant Schiff base linkages to lysines close to the normal linkage in the structure of bacteriorhodopsin. In either case, the retinal does not leave its binding site. This last point severely limits the possible arrangements of the amino acid sequence in the bacteriorhodopsin tertiary structure and clearly distinguishes two models that are consistent with all criteria.
在对细菌视紫红质中的视黄叉-赖氨酸席夫碱键进行化学还原后，视黄基残基共价连接到赖氨酸-216（可能有一小部分连接到赖氨酸-172）或同时连接到赖氨酸-216（172）和赖氨酸-40/41。连接位点（在赖氨酸-216上可达100%；在赖氨酸-40/41上可达70%）取决于样品是在光照下还是黑暗中被还原，样品是适应光照还是适应黑暗，以及温度。吸光度和圆二色光谱表明，视黄基残基在光照下还原后仍处于其原始结合位点。因此，不同的连接位点可能反映了光反应循环期间或光/暗适应期间发生的变化，或者是细菌视紫红质结构中与正常连接接近的赖氨酸上偶然的生理上无关的席夫碱键的还原。无论哪种情况，视黄醛都不会离开其结合位点。最后这一点严重限制了细菌视紫红质三级结构中氨基酸序列的可能排列，并清楚地区分了符合所有标准的两种模型。
