Anion sensitivity and spectral tuning of cone visual pigments in situ.
Anion sensitivity and spectral tuning of cone visual pigments in situ.
复制标题
视锥细胞原位视色素的阴离子敏感性和光谱调谐。
DOI：
10.1073/pnas.89.19.9181
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发表时间：
1992
影响因子：
11.1
通讯作者：
Harosi,FI
中科院分区：
文献类型：
--
作者：
Kleinschmidt,J;Harosi,FI
用显微分光光度法测定了四种鱼类和一种两栖动物的视锥外节中阴离子对天然视色素吸收光谱的影响。在所有测试的物种中，长波吸收锥体色素对阴离子敏感，它们的λ max可以在55 nm的范围内调谐，这取决于存在的阴离子的身份。Cl-和Br-是唯一在无阴离子条件下通过λ max红移产生天然色素光谱的阴离子。溶性阴离子如NO3-、SCN-、BF4-和ClO4-引起lambda max的大量渐变蓝移。色素上Cl-和ClO4-结合位点的表观Kd约为2mm。结合先前对爬行类、鸟类和两栖类三种视觉色素的研究结果，我们的结果支持了所有长波吸收脊椎动物视觉色素都部分通过氯离子结合而进行光谱调谐的假设。我们认为阴离子调谐的位置在发色团的质子化席夫碱附近，其对偶离子可能是复杂的，并且包括Cl-作为交换阴离子。这种反离子结构可能类似于光驱动的氯泵盐视紫红质。
We tested the effect of anions on the absorbance spectrum of native visual pigments as measured by microspectrophotometry in individual cone outer segments of four species of fish and one species of amphibian. In all species tested, the long-wavelength-absorbing cone pigments were anion sensitive, and their lambda max could be tuned over a range of 55 nm depending on the identity of the anion present. Cl- and Br- were the only anions that produced native pigment spectra by red shifting lambda max from its value under anion-free conditions. Lyotropic anions such as NO3-, SCN-, BF4-, and ClO4- caused substantial and graded blue shifts of lambda max. The apparent Kd of binding sites on the pigment for Cl- and for ClO4- was approximately 2 mM. Taken together with previous findings on three visual pigments from the reptilian, avian, and amphibian classes, our results support the hypothesis that all long-wavelength-absorbing vertebrate visual pigments are spectrally tuned in part through the binding of a chloride ion. We propose that the site of anion tuning is near the protonated Schiff base of the chromophore, whose counterion may be complex and include Cl- as an exchangeable anion. This counterion configuration may resemble the one present in the light-driven Cl- pump halorhodopsin.