A tight coupling between beta(2)Y97 and beta(2)F200 of the GABA(A) receptor mediates GABA binding

作者：Tran Phu N^*; Laha Kurt T; Wagner David A

来源：Journal of Neurochemistry, 2011, 119(2): 283-293.

DOI：10.1111/j.1471-4159.2011.07409.x

The GABA(A) receptor is an oligopentameric chloride channel that is activated via conformation changes induced upon the binding of the endogenous ligand, GABA, to the extracellular inter-subunit interfaces. Although dozens of amino acid residues at the alpha/beta interface have been implicated in ligand binding, the structural elements that mediate ligand binding and receptor activation are not yet fully described. In this study, double-mutant cycle analysis was employed to test for possible interactions between several arginines (alpha(1)R67, alpha(1)R120, alpha(1)R132, and beta(2)R207) and two aromatic residues (beta(2)Y97 and beta(2)F200) that are present in the ligand-binding pocket and are known to influence GABA affinity. Our results show that neither alpha(1)R67 nor alpha(1)R120 is functionally coupled to either of the aromatics, whereas a moderate coupling exists between alpha(1)R132 and both aromatic residues. Significant functional coupling between beta(2)R207 and both beta(2)Y97 and beta(2)F200 was found. Furthermore, we identified an even stronger coupling between the two aromatics, beta(2)Y97 and beta(2)F200, and for the first time provided direct evidence for the involvement of beta(2)Y97 and beta(2)F200 in GABA binding. As these residues are tightly linked, and mutation of either has similar, severe effects on GABA binding and receptor kinetics, we believe they form a single functional unit that may directly coordinate GABA.

• 出版日期2011-10