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首页> 外文期刊>Biochemistry >Photosensitivities of Rhodopsin Mutants with a Displaced Counterion
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Photosensitivities of Rhodopsin Mutants with a Displaced Counterion

机译：视紫红质突变体的抗衡离子的光敏性。

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摘要

Visual pigments consist of a protein moiety opsin and an 11-cis-retinal chromophore that is cova-nlently bound to the opsin via a Schiff base linkage. They have a high photosensitivity, which can be attributednto the high probability of photon absorption and the high photoisomerization quantum yield of the retinalnchromophore. Both of these parameters are regulated by the opsin, though the precisemechanismis unknown.Wenpreviously found that counterion residue E113, which stabilizes the proton on the Schiff base, is involved innthe efficient photoisomerization in vertebrate visual pigments. To test the positional effect of the counterionnon the photon absorption and the photoisomerization, we measured the photosensitivities of a set of mutantsnof bovine rhodopsin in which the counterion was displaced to position 90, 94, 117, or 292. The molarnextinction coefficient was reduced in many of the mutants, leading to reductions in the photosensitivity fornmonochromatic lights.However, the oscillator strength, the probability of photon absorption integrated overnthe entire wavenumber range of the absorption band, was relatively similar among the mutants and the wildntype. In addition, the quantum yields of the mutants were not markedly different from that of the wild type.nThese results indicate that the counterion does not need to be located at position 113 for a high photo-nsensitivity for natural light. Interestingly, all of the mutants exhibited greatly increased hydroxylaminensensitivity. This result suggests that the counterion in vertebrate visual pigments is optimally located for thenstability of the Schiff base linkage
机译：视觉色素由蛋白部分视蛋白和11-顺-视网膜发色团组成，该发色团通过席夫碱键与视蛋白紧密结合。它们具有高的光敏性，这可以归因于视网膜发色团的高光子吸收率和高光异构化量子产率。这两个参数均由视蛋白调节，尽管其确切机理尚不清楚。先前发现，稳定希夫碱上质子的抗衡离子残基E113与脊椎动物视觉色素的有效光异构化有关。为了测试抗衡离子对光子吸收和光异构化的位置影响，我们测量了一组牛视紫红质突变体的光敏性，其中抗衡离子被置换到位置90、94、117或292。在许多情况下，消光消光系数降低了然而，在突变体和野生型之间，振荡器强度，光子吸收的概率在吸收带的整个波数范围内积分的概率相对相似。此外，突变体的量子产率与野生型没有显着差异。n这些结果表明，对于自然光具有很高的光敏性，抗衡离子不必位于位置113。有趣的是，所有突变体均表现出大大提高的羟胺敏感性。该结果表明，脊椎动物视觉色素中的抗衡离子位于席夫碱键的稳定性的最佳位置。

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  • 来源
    《Biochemistry》 |2010年第47期|p.10089-10097|共9页
  • 作者

    Kei Tsutsui and Yoshinori Shichida;

  • 作者单位

    Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.‡Present address: Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka 565-0871, Japan.;

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