Reconstitution of ancestral green visual pigments of zebrafish and molecular mechanism of their spectral differentiation
Reconstitution of ancestral green visual pigments of zebrafish and molecular mechanism of their spectral differentiation
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DOI：
10.1093/molbev/msi086
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发表时间：
2005-04-01
影响因子：
10.7
通讯作者：
Kawamura, S
中科院分区：
文献类型：
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作者：
Chinen, A;Matsumoto, Y;Kawamura, S
我们之前报道过斑马鱼有四个串联重复的绿色（RH2）视蛋白基因（RH2-1、RH2-2、RH2-3 和 RH2-4）。用11-顺式视黄醛重构的四种感光色素的吸收光谱差异很大，其峰值吸收光谱分别为467、476、488和505 nm。在本研究中，我们通过基于似然的贝叶斯统计推断了斑马鱼 RH2 视蛋白的祖先氨基酸 (aa) 序列，并通过定点诱变重建了祖先视蛋白。四种斑马鱼 RH2 色素的祖先色素 (A1) 以及 RH2-3 和 RH2-4 的祖先色素 (A3) 在 506 nm 处显示 gimel(max)，而 RH2-1 和 RH2-2 的祖先色素 (A2) 在 474 nm 处显示 gimel(max)，表明进化谱系 At 到 A2 上发生了向较短波长的光谱偏移，A2 到RH2-1 为 7 nm，A3 为 RH2-3 为 18 nm。色素嵌合体和定点诱变揭示了残基 122 (E122Q) 处的谷氨酸到谷氨酰胺取代对 A1 到 A2 和 A3 到 RH2-3 光谱位移的巨大贡献（类似于 15 nm）。然而，其余的光谱差异似乎是由多种氨基酸替代物的复杂交互效应造成的，每种替代物仅具有较小的光谱贡献（1-3 nm）。这四种斑马RH2色素几乎覆盖了脊椎动物RH2色素的整个gimel(max)分布范围，并为研究脊椎动物RH2光谱调谐机制提供了一个极好的模型。
We previously reported that zebrafish have four tandemly duplicated green (RH2) opsin genes (RH2-1, RH2-2, RH2-3, and RH2-4). Absorption spectra vary widely among the four photopigments reconstituted with 11-cis retinal, with their peak absorption spectra being 467, 476, 488, and 505 nm, respectively. In this study, we inferred the ancestral amino acid (aa) sequences of the zebrafish RH2 opsins by likelihood-based Bayesian statistics and reconstituted the ancestral opsins by site-directed mutagenesis. The ancestral pigment (A1) to the four zebrafish RH2 pigments and that (A3) to RH2-3 and RH2-4 showed gimel(max) at 506 nm, while that (A2) to RH2-1 and RH2-2 showed gimel(max) at 474 nm, indicating that a spectral shift had occurred toward the shorter wavelength on the evolutionary lineages At to A2 by 32 nm, A2 to RH2-1 by 7 nm, and A3 to RH2-3 by 18 nm. Pigment chimeras and site-directed mutagenesis revealed a large contribution (similar to 15 nm) of glutamic acid to glutamine substitution at residue 122 (E122Q) to the A1 to A2 and A3 to RH2-3 spectral shifts. However, the remaining spectral differences appeared to result from complex interactive effects of a number of aa replacements, each of which has only a minor spectral contribution (1-3 nm). The four zebratish RH2 pigments cover nearly an entire range of gimel(max) distribution among vertebrate RH2 pigments and provide an excellent model to study spectral tuning mechanisms of RH2 in vertebrates.