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首页> 外文期刊>Biochemistry >EFFECT OF CHLORIDE ON THE THERMAL REVERSE REACTION OF INTERMEDIATES OF IODOPSIN
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EFFECT OF CHLORIDE ON THE THERMAL REVERSE REACTION OF INTERMEDIATES OF IODOPSIN

机译：氯化物对碘蛋白酶中间产物的热逆反应的影响

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Among the intermediates in the bleaching process of iodopsin, a chicken red-sensitive cone visual pigment, the bathe and meta I intermediates (bathe and meta I) formed at low temperatures revert to the original iodopsin by thermal reactions [Yoshizawa & Wald (1967) Nature 214, 566-572; Imamoto, Imai, Yoshizawa, & Shichida (1994) FEES Lett, 354, 165-168]. In order to elucidate the relationship between Cl- binding to iodopsin and these reverse reactions, we have prepared a sample of iodopsin whose Cl--binding site is vacant (anion-unbound iodopsin) and compared the thermal reactions of its bathe and meta I intermediates with those of Cl--bound (native) and nitrate-bound iodopsins. The reverse reaction from bathe is observed in both Cl--bound and anion-unbound iodopsins, while the reaction from meta I is observed only in Cl--bound iodopsin. These results indicate that Cl- binding is indispensable for the reverse reaction from meta I, but not from bathe. The reverse reaction from meta I has been further investigated as a function of Cl- concentration, and the dissociation constant of Cl- in meta I is estimated to be similar to 20 mM. This value is about 200 times larger than that of iodopsin (0.1 mM), and close to the physiological Cl- concentration in photoreceptor cells, suggesting that Cl- could be released from the protein moiety during the bleaching of iodopsin.
机译：碘伏素的漂白过程中的一种中间体，一种鸡红色敏感的锥状视觉颜料，在低温下形成的浴液和间位中间体（浴液和间位I）通过热反应还原为原始的碘蛋白[Yoshizawa＆Wald（1967）自然214，566-572;今元，今井，吉泽和七田（1994），FEES Lett，354，165-168]。为了阐明氯与碘的结合与这些逆反应之间的关系，我们制备了碘与氯的结合位点为空的阴离子（未结合的碘），并比较了其浴液和间位中间体的热反应。与氯结合的（天然）和硝酸盐结合的碘蛋白在结合氯的和未结合阴离子的碘蛋白酶中都观察到了浴的逆反应，而仅在结合氯的碘素中观察到了间位I的反应。这些结果表明Cl-结合对于来自meta I的逆反应是必不可少的，但是对于来自浴的逆反应不是必不可少的。来自Meta I的逆反应已作为Cl-浓度的函数进行了进一步研究，估计Meta I中Cl-的解离常数类似于20 mM。该值是碘蛋白（0.1 mM）的200倍左右，并且接近感光细胞中的生理Cl-浓度，这表明在碘蛋白漂白过程中Cl-可能从蛋白质部分释放出来。

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