Ulfers Amy L, McMurry Jonathan L, Miller Alexander, Wang Ligong, Kendall Debra A, Mierke Dale F
Department of Molecular Pharmacology, Division of Biology and Medicine, Brown University, Providence, Rhode Island 02912, USA.
Protein Sci. 2002 Oct;11(10):2526-31. doi: 10.1110/ps.0218402.
The structure of the C-terminal region of the third cytoplasmic loop (IC3) of the cannabinoid receptor one (CB1) bound to G(alphai1) has been determined using transferred nuclear Overhauser effects (NOEs). The wild-type IC3 sequence is helical when associated with G(alphai1). In contrast, a peptide containing the amino-acid inversion, Ala(341)-Leu(342) adopts a single turn. These findings correlate with the attenuated G(i) association of CB1 with the Ala(341)-Leu(342) mutation previously observed in vivo and the diminished stimulation of G(alphai1) GTPase activity by the corresponding peptide demonstrated in vitro here. These results, the first to report the structure of a GPCR domain while associated with G protein, imply the C-terminus of CB1 IC3, a region with high-sequence conservation among G-protein coupled receptors, must be helical for efficient coupling and activation of the G(i) protein.
通过转移核Overhauser效应（NOE）确定了与G（αi1）结合的大麻素受体1（CB1）第三细胞质环（IC3）C端区域的结构。野生型IC3序列与G（αi1）结合时呈螺旋状。相比之下，含有氨基酸倒置Ala（341）-Leu（342）的肽段呈单圈结构。这些发现与之前在体内观察到的CB1与Ala（341）-Leu（342）突变体G（i）结合减弱以及此处体外实验证明的相应肽段对G（αi1）GTP酶活性刺激减弱相关。这些结果首次报道了GPCR结构域与G蛋白结合时的结构，表明CB1 IC3的C端，即G蛋白偶联受体中具有高度序列保守性的区域，必须呈螺旋状才能有效偶联并激活G（i）蛋白。
