Wang Z, Asenjo A B, Oprian D D
Graduate Department of Biochemistry, Brandeis University, Waltham, Massachusetts 02254.
Biochemistry. 1993 Mar 9;32(9):2125-30. doi: 10.1021/bi00060a001.
Chloride ions are known to bind and alter the absorption spectra of some but not all visual pigments. In this report, the human red and green color vision pigments are shown to bind Cl- and to undergo a large red shift in their absorption maxima. Mutation of 18 different positively charged amino acids in these pigments identified two residues, His197 and Lys200, in the Cl(-)-binding site. His197 and Lys200 are strictly conserved in all long-wavelength cone pigments but are absent in all rhodopsins and short-wavelength cone pigments. This fact suggests that the evolutionary branch of the long-wavelength pigments was established when an ancestral pigment acquired the ability to bind Cl- and, as a result, shift the absorption maximum to longer wavelengths.
已知氯离子会结合并改变某些而非所有视觉色素的吸收光谱。在本报告中，人类红色和绿色视觉色素显示出能结合氯离子，并使其吸收最大值发生大幅红移。对这些色素中18种不同带正电荷氨基酸的突变分析确定了氯离子结合位点中的两个残基，即His197和Lys200。His197和Lys200在所有长波长视锥色素中严格保守，但在所有视紫红质和短波长视锥色素中不存在。这一事实表明，当一种祖先色素获得结合氯离子的能力并因此将吸收最大值移向更长波长时，长波长色素的进化分支就已确立。
