Transverse location of the retinal chromophore of rhodopsin in rod outer segment disc membranes.
Transverse location of the retinal chromophore of rhodopsin in rod outer segment disc membranes.
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DOI：
10.1016/0022-2836(82)90422-3
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发表时间：
1982-01
影响因子：
5.6
通讯作者：
David D. Thomas;L. Stryer
中科院分区：
文献类型：
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作者：
David D. Thomas;L. Stryer
用扩散增强荧光能量转移技术研究了牛视网膜视杆外节感光细胞膜的结构。荧光能量供体为Tb~(3+)螯合二吡啶甲酸酯，受体为视紫红质11-顺式视网膜发色团。由于Tb施主的激发态寿命较长(~2ms)，在这些实验中达到了能量传递的快速扩散极限。在这些条件下，能量转移对供体和受体之间最接近的距离a非常敏感(Thomaset al.，1978)。在这种络合物存在的情况下，通过超声作用于盘膜，并在凝胶过滤柱层析这种混合物，制备了在其内部水空间中含有二吡啶甲酸Tb的囊泡。视紫红质在这些小泡中的侧化程度与天然视盘膜中的相同。在该样品中，Tb向视网膜的转移效率为43%。对于R0值为46.7？和平均囊泡直径为650？的情况，这相当于囊泡内部水空间的平均值为22？通过在已经形成的囊泡悬浮液中加入二吡啶甲酸铽来确定最接近外部水空间的距离为28？这些数值表明，视网膜生色团远离视盘膜的两个水表面.因此，视网膜发色团的横向位置靠近盘膜疏水核心的中心。这些发现表明，光异构化引起的构象变化在视紫红质内通过至少20？的距离传递，从而在视觉兴奋中触发后续事件。
Diffusion-enhanced fluorescence energy transfer was used to study the structure of photoreceptor membranes from bovine retinal rod outer segments. The fluorescent energy donor was Tb3+chelated to dipicolinate and the acceptor was the 11-cisretinal chromophore of rhodopsin in vesicles made from disc membranes. The rapid-diffusion limit for energy transfer was attained in these experiments because of the long excited state lifetime of the terbium donor (~2 ms). Under these conditions, energy transfer is very sensitive toa, the distance of closest approach between the donor and acceptor (Thomaset al., 1978). Vesicles containing terbium dipicolinate in their inner aqueous space were prepared by sonicating disc membranes in the presence of this chelate and chromatographing this mixture on a gel filtration column. The sidedness of rhodopsin in these vesicles was the same as in native disc membranes. The transfer efficiency from terbium to retinal in this sample was 43%. For anR0value of 46.7 Å and an average vesicle diameter of 650 Å, this corresponds to anavalue of 22 Å from the inner aqueous space of the vesicle. The distance of closest approach from the external aqueous space, determined by adding terbium dipicolinate to a suspension of already formed vesicles, was found to be 28 Å. These values ofashow that the retinal chromophore is far from both aqueous surfaces of the disc membrane. Hence, the transverse location of the retinal chromophore is near the center of the hydrophobic core of the disc membrane. These findings suggest that conformational changes induced by photoisomerization are transmitted through a distance of at least 20 Å within rhodopsin to trigger subsequent events in visual excitation.