Coupling of Protonation Switches During Rhodopsin Activation †
Coupling of Protonation Switches During Rhodopsin Activation †
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视紫红质激活过程中质子化开关的耦合 †
DOI：
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发表时间：
2007
影响因子：
3.3
通讯作者：
F. Siebert
中科院分区：
文献类型：
--
作者：
R. Vogel;T. Sakmar;M. Sheves;F. Siebert
最近的研究涉及傅里叶变换红外光谱和发色团修饰和定点突变的组合的视紫红质的活化机制揭示了两个质子化开关之间的变构偶联。特别是，全反式视网膜发色团的环和9-甲基基团用于耦合两个质子依赖性激活步骤：通过保守的ERY（Glu-Arg-Tyr）基序周围的跨膜（TM）螺旋3和6之间的细胞质网络的质子吸收，以及破坏视网膜质子化席夫碱（PSB）和受体TM核心中的蛋白质互补物之间的盐桥。缺少环或9-甲基的视网膜类似物只是部分激动剂-无活性的Meta I和活性的Meta II光产物状态之间的构象平衡向Meta I移动。本文报道了一种人工色素的制备方法，该方法去除了视网膜环，并通过对视网膜多烯中的C14进行修饰，削弱了PSB盐桥。这些修饰消除了质子开关的变构偶联，并导致与去质子化的席夫碱（Meta ISB）的稳定的Meta I状态。由于PSB盐桥的破坏，该状态具有部分Meta II样构象，但仍然缺乏最终转变为Meta II的细胞质质子摄取反应特征。由于已知天然视紫红质的活化涉及在形成Meta II之前视网膜席夫碱的去质子化，因此该Meta ISB状态可用作原型G蛋白偶联受体活化途径中关键瞬时物质的结构表征的模型。
Recent studies of the activation mechanism of rhodopsin involving Fourier‐transform infrared spectroscopy and a combination of chromophore modifications and site‐directed mutagenesis reveal an allosteric coupling between two protonation switches. In particular, the ring and the 9‐methyl group of the all‐trans retinal chromophore serve to couple two proton‐dependent activation steps: proton uptake by a cytoplasmic network between transmembrane (TM) helices 3 and 6 around the conserved ERY (Glu‐Arg‐Tyr) motif and disruption of a salt bridge between the retinal protonated Schiff base (PSB) and a protein counterion in the TM core of the receptor. Retinal analogs lacking the ring or 9‐methyl group are only partial agonists—the conformational equilibrium between inactive Meta I and active Meta II photoproduct states is shifted to Meta I. An artificial pigment was engineered, in which the ring of retinal was removed and the PSB salt bridge was weakened by fluorination of C14 of the retinal polyene. These modifications abolished allosteric coupling of the proton switches and resulted in a stabilized Meta I state with a deprotonated Schiff base (Meta ISB). This state had a partial Meta II‐like conformation due to disruption of the PSB salt bridge, but still lacked the cytoplasmic proton uptake reaction characteristic of the final transition to Meta II. As activation of native rhodopsin is known to involve deprotonation of the retinal Schiff base prior to formation of Meta II, this Meta ISB state may serve as a model for the structural characterization of a key transient species in the activation pathway of a prototypical G protein‐coupled receptor.
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影响因子：
56.9
作者：
E. Zhukovsky;D. Oprian
通讯作者：
E. Zhukovsky;D. Oprian
DOI：
10.1073/pnas.86.21.8309
发表时间：
1989-11-01
影响因子：
11.1
作者：
SAKMAR, TP;FRANKE, RR;KHORANA, HG
通讯作者：
KHORANA, HG
变视紫红质中发色团-蛋白质相互作用的模拟色素研究。
影响因子：
2.9
作者：
Renk,G;Crouch,RK
通讯作者：
Crouch,RK
DOI：
10.1073/pnas.0402848101
发表时间：
2004-07-06
影响因子：
11.1
作者：
Patel, AB;Crocker, E;Smith, SO
通讯作者：
Smith, SO