图3-7：低分辨率GABAB-G复合物的鉴定。（a,b）两种通过GB2

图3-7：低分辨率GABAB-G复合物的鉴定。（a,b）两种通过GB2亚基偶联G蛋白的模式，分别为B2a状态（a）和B2a状态（b）。（c）一种通过GB1亚基偶联G蛋白的模式，为B1状态。（d）GABAB结合G蛋白的模式主要是通过由三个胞内环组成的口袋。（e）以结合G蛋白的TM作为参照，将B1状态的结构分别和B2a,B2b状态的结构比较，两个G蛋白会产生较大位阻，这可以解释GABAB和G蛋白为2:1的关系。

Figure 3-7: identification of low resolution gabab-g complex. (a, b) two modes of coupling G protein through GB2 subunit, B2A state (a) and B2A state (b), respectively. (c) A mode of coupling G protein through GB1 subunit, which is in B1 state. (d) The pattern of GABAB binding to G protein is mainly through a pocket composed of three intracellular rings. (e) Taking TM binding to G protein as a reference, comparing the structure of B1 state with that of B2A and B2B states respectively, the two G proteins will produce large steric hindrance, which can explain the 2:1 relationship between GABAB and G protein.

Figure 3-7: Identification of low-resolution GABAB-G complex. (a,b) Two modes of coupling G protein through GB2 subunit, namely B2a state (a) and B2a state (b). (c) A mode of coupling G protein through GB1 subunit, which is in B1 state. (d) The mode of d)GABAB binding to G protein is mainly through the pocket consisting of three inner rings. (e) Comparing the structure of B1 state with that of B2A and B2B state, respectively, with TM bound to G protein as a reference, the two G proteins will have larger steric hindrance, which can explain the 2:1 relationship between GABAB and G protein.