Constitutive activity of a UV cone opsin.
Constitutive activity of a UV cone opsin.
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紫外视锥细胞视蛋白的组成活性。
DOI：
10.1016/j.febslet.2005.12.002
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发表时间：
2006
期刊：
影响因子：
3.5
通讯作者：
Kono,Masahiro
中科院分区：
文献类型：
--
作者：
Kono,Masahiro
脊椎动物视色素蛋白在第三跨膜螺旋中含有保守的羧酸残基。在视紫红质中，Glu113与Lys296上的11顺式视网膜形成的带正电的席夫碱形成抗离子。激活涉及到打破这个离子对。在UV锥体颜料中，视黄基席夫碱是未质子化的，因此不存在这样的盐桥；然而，色素在黑暗中是不活跃的。对应于视紫红质的Glu113的Glu108突变为Gln，产生了一种在黑暗中保持不活跃的色素。然而，野生型和突变型的脱辅基蛋白都具有结构性活性，其中突变型的活性显著高于野生型。因此，保存UV色素第三螺旋中带负电荷的谷氨酸的一个重要作用是以类似于视紫红质的方式保持较不活跃的视蛋白。在没有盐桥的情况下，配体结合本身就足以使其失活。
Vertebrate visual pigment proteins contain a conserved carboxylic acid residue in the third transmembrane helix. In rhodopsin, Glu113 serves as a counterion to the positively charged protonated Schiff base formed by 11-cis retinal attached to Lys296. Activation involves breaking of this ion pair. In UV cone pigments, the retinyl Schiff base is unprotonated, and hence such a salt bridge is not present; yet the pigment is inactive in the dark. Mutation of Glu108, which corresponds to rhodopsin’s Glu113, to Gln yields a pigment that remains inactive in the dark. The apoproteins of both the wild-type and mutant, however, are constitutively active with the mutant being of significantly higher activity. Thus, one important role for preserving the negatively charged glutamate in the third helix of UV pigments is to maintain a less active opsin in a manner similar to rhodopsin. Ligand binding itself in the absence of a salt bridge is sufficient for deactivation.