Efficient coupling of transducin to monomeric rhodopsin in a phospholipid bilayer
Efficient coupling of transducin to monomeric rhodopsin in a phospholipid bilayer
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DOI：
10.1074/jbc.m703346200
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发表时间：
2008-02-15
影响因子：
4.8
通讯作者：
Sunahara, Roger K.
中科院分区：
文献类型：
--
作者：
Whorton, Matthew R.;Jastrzebska, Beata;Sunahara, Roger K.
G蛋白偶联受体（gpcr）是7种跨膜结构域蛋白，它们通过质膜转导细胞外信号并偶联到G蛋白的异源三聚体家族。像大多数内在膜蛋白一样，gpcr具有寡聚化的能力，其功能仅在少数几种不同的受体系统中得到证实。了解低聚物功能的一个挑战是在膜环境中无法分离单体和低聚受体复合物。在这里，我们报告了牛视紫红质，在视网膜中表达的GPCR，重组成载脂蛋白a - i磷脂颗粒，来源于高密度脂蛋白（HDL）。我们证明，视紫红质，当纳入这些10纳米重组HDL （rHDL）颗粒时，是单体的和功能性的。视紫红质。rHDL在光激活和活性形式后视紫红质II的形成方面保持适当的光谱特性。此外，在天然膜中的视紫红质和rHDL颗粒中的视紫红质之间，后视紫红质II衰变的动力学相似。单体视紫红质的光活化。rHDL也导致转导蛋白的快速激活，其速度与天然杆外段相当，比洗涤剂胶束中的视紫红质快20倍。这些数据表明，单体视紫红质是G蛋白激活的最小功能单位，而寡聚化并不是这个过程所必需的。
G protein-coupled receptors (GPCRs) are seven transmembrane domain proteins that transduce extracellular signals across the plasma membrane and couple to the heterotrimeric family of G proteins. Like most intrinsic membrane proteins, GPCRs are capable of oligomerization, the function of which has only been established for a few different receptor systems. One challenge in understanding the function of oligomers relates to the inability to separate monomeric and oligomeric receptor complexes in membrane environments. Here we report the reconstitution of bovine rhodopsin, a GPCR expressed in the retina, into an apolipoprotein A-I phospholipid particle, derived from high density lipoprotein (HDL). We demonstrate that rhodopsin, when incorporated into these 10 nm reconstituted HDL (rHDL) particles, is monomeric and functional. Rhodopsin . rHDL maintains the appropriate spectral properties with respect to photoactivation and formation of the active form, metarhodopsin II. Additionally, the kinetics of metarhodopsin II decay is similar between rhodopsin in native membranes and rhodopsin in rHDL particles. Photoactivation of monomeric rhodopsin . rHDL also results in the rapid activation of transducin, at a rate that is comparable with that found in native rod outer segments and 20-fold faster than rhodopsin in detergent micelles. These data suggest that monomeric rhodopsin is the minimal functional unit in G protein activation and that oligomerization is not absolutely required for this process.