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首页> 外文期刊>Biochemistry >A pharaonis Phoborhodopsin Mutant with the Same Retinal Binding Site Residues As in Bacteriorhodopsin
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A pharaonis Phoborhodopsin Mutant with the Same Retinal Binding Site Residues As in Bacteriorhodopsin

机译：具有与细菌视紫红质相同的视网膜结合位点残基的法老氏菌视紫红质突变体。

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摘要

Pharaonis phoborhodopsin (ppR, also called pharaonis sensory rhodopsin II, psR-II) is a photoreceptor for negative phototaxis in Natronobacterium pharaonis. ppR has a blue-shifted absorption maximum (500 nm) relative those of other archaeal rhodopsins such as the proton-pump bacteriorhodopsin (BR; 570 nm). Among the 25 amino acids that are within 5 A of the retinal chromophore, 10 are different in BR and ppR, and they are presumed to be crucial in determining the color of their chromophores. However, the spectral red shift in a multiple mutant of ppR, in which the retinal binding site was made similar to that of BR (BR/ppR), was smaller than 40% (#lambda#_max = 524 nm) than expected. In the paper presented here, we report on low-temperature Fourier transform infrared (FTIR) spectroscopy of BR/ppR, and compare the infrared spectral changes before and after photoisomerization with those for ppR and BR. The C-C stretch and hydrogen out-of-plane (HOOP) vibrations of BR/ppR were similar to those of BR, suggesting that the surrounding protein moiety of BR/ppR becomes like BR. However, BR/ppR exhibited a unique IR band regarding the hydrogen bond of the protonted Schiff bvase. It has been known that ppR has a stronger hydrogen bond for the Schiff base than BR as judged from the frequency difference between their C=NH and C=ND stretches. We now find that replacement of the 10 amino acids of BR with ppR (BR/ppR) does not weaken the hydrogen bond of the Schiff base. REather, the hydrogen bond in BR/ppR is stronger than that in the native ppR. We conclude that the principal factor of the smaller than expected opsin shift in BR/ppR is the strong association of the Schiff base with the surrounding counterion coplex.
机译：Pharaonis phoborhodopsin（ppR，也称为法老氏感觉性视紫红质II，psR-II）是法老氏杆菌中负趋光性的光感受器。相对于其他古细菌视紫红质（例如质子泵细菌视紫红质（BR; 570 nm）），ppR具有最大蓝移吸收峰（500 nm）。在视网膜发色团5 A内的25个氨基酸中，BR和ppR分别有10个不同，并且推测它们对于确定其发色团的颜色至关重要。但是，在ppR的多个突变体中光谱红移比预期的要小40％（＃lambda＃_max = 524 nm），在该突变体中，视网膜结合位点类似于BR（BR / ppR）。在此处介绍的论文中，我们报道了BR / ppR的低温傅立叶变换红外（FTIR）光谱，并比较了光异构化前后的红外光谱变化与ppR和BR的红外光谱变化。 BR / ppR的C-C拉伸和氢平面外（HOOP）振动与BR相似，这表明BR / ppR的周围蛋白质部分变得像BR。但是，BR / ppR在质子化席夫bvase的氢键方面表现出独特的IR带。从它们的C ＝ NH和C ＝ ND延伸之间的频率差判断，已知ppR对Schiff碱的氢键比BR强。现在我们发现用ppR（BR / ppR）取代BR的10个氨基酸不会削弱席夫碱的氢键。相反，BR / ppR中的氢键比天然ppR中的氢键强。我们得出的结论是，BR / ppR中视蛋白移位小于预期的主要原因是席夫碱与周围抗衡离子复合物的强结合。

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