Comparison of the mechanism on functional expression of diverged rhodopsins by using their mutants

视紫红质家族的成员至少分为五个亚类。本研究对文昌鱼GO偶联视紫红质和Peropsin进行了研究，以了解GO偶联视紫红质和Peropsin对分化视紫红质功能表达的作用机制；具体地说，1.作为对抗离子的氨基酸残基的比较2.Go偶联视紫红质和脊椎动物视紫红质G蛋白激活机制的比较，然后3.Peropsin的生理功能的研究。结果：1.与牛视紫红质不同的是，与视黄色素一样，属于GO偶联视紫红质和Peropinins的文昌鱼在第二细胞外回路第181位有谷氨酸拮抗剂。建立了文昌鱼视紫红质G蛋白激活能力的检测方法，与脊椎动物视紫红质G蛋白激活机制进行了严格的比较。发色团的高效液相色谱分析表明，Peropsin以全反式视网膜为发色团，光引起从全反式到11-顺式的异构化。这一发现表明，Peropsin的功能类似于视黄素和RGR的光异构酶。

The members of rhodopsin family are divided into at least five subgroups. In this study, the amphioxus Go-coupled rhodopsin and peropsin were investigated to understand the mechanism on the functional expression of diverged rhodopsins ; specifically, 1. comparison of the amino acid residue which functions as counterion 2.comparison of G protein activation mechanism between Go-coupled rhodopsin and vertebrate rhodopsins, and then 3. investigation of physiological function of peropsin.Results :1. Unlike bovine rhodopsin but like retinochrome, amphioxus relatives belonging to the groups of Go-coupled rhodopsins and peropsins have the glutamic acid counterions at position 181 in the 2nd extracellular loop.2. We established the procedures to measure the G protein activation ability of the amphioxus rhodopsin to strictly compare the G protein activation mechanism with vertebrate rhodopsins.3. HPLC analyses of chromophore retinal revealed that peropsin has all-trans-retinal as the chromophore, and light causes the isomerization from all-trans to 11-cis. This finding suggested that peropsin functions as photoisomerase like retinochrome and RGR.