Effect of carboxylic acid side chains on the absorption maximum of visual pigments.
Effect of carboxylic acid side chains on the absorption maximum of visual pigments.
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DOI：
10.1126/science.2573154
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发表时间：
1989-11
期刊：
影响因子：
56.9
通讯作者：
E. Zhukovsky;D. Oprian
中科院分区：
文献类型：
--
作者：
E. Zhukovsky;D. Oprian
视色素的最大吸收是由11-顺式-视网膜发色团与蛋白质的膜嵌入区域中的带电羧酸侧链的相互作用决定的，这一提议已经通过突变被认为埋在视紫红质中的5个天冬氨酸和谷氨酸残基进行了测试。将Glu 113改变为Gln导致吸收最大值从500纳米到380纳米的显著偏移，发色团的质子化Schiff碱的pKa（酸度常数）降低到约6，并且与羟胺的反应性大大增加。因此，Glu 113似乎是质子化席夫碱的抗衡离子。可见色素中的波长调制显然不受与羧酸残基的静电相互作用的控制，而不是相反。
The proposal that the absorption maximum of the visual pigments is governed by interaction of the 11-cis-retinal chromophore with charged carboxylic acid side chains in the membrane-embedded regions of the proteins has been tested by mutating five Asp and Glu residues thought to be buried in rhodopsin. Changing Glu113 to Gln causes a dramatic shift in the absorption maximum from 500 nanometers to 380 nanometers, a decrease in the pKa (acidity constant) of the protonated Schiff base of the chromophore to about 6, and a greatly increased reactivity with hydroxylamine. Thus Glu113 appears to be the counterion to the protonated Schiff base. Wavelength modulation in visual pigments apparently is not governed by electrostatic interaction with carboxylate residues, other than the counterion.