| First Author | Price KL | Year | 2008 |
| Journal | Biochemistry | Volume | 47 |
| Issue | 24 | Pages | 6370-7 |
| PubMed ID | 18498149 | Mgi Jnum | J:138342 |
| Mgi Id | MGI:3805047 | Doi | 10.1021/bi800222n |
| Citation | Price KL, et al. (2008) A hydrogen bond in loop A is critical for the binding and function of the 5-HT3 receptor. Biochemistry 47(24):6370-7 |
| abstractText | The binding sites of Cys-loop receptors are formed from at least six loops (A-F). Here we have used mutagenesis, radioligand binding, voltage clamp electrophysiology, and homology modeling to probe the role of two residues in loop A of the 5-HT3 receptor: Asn128 and Glu129. The data show that substitution of Asn128, with a range of alternative natural and unnatural amino acids, changed the EC50 (from approximately 10-fold more potent to approximately 10-fold less potent than that of the wild type), increased the maximal peak current for mCPBG compared to 5-HT (R max) 2-19-fold, and decreased n H, indicating this residue is involved in receptor gating; we propose Asn128 faces away from the binding pocket and plays a role in facilitating transitions between conformational states. Substitutions of Glu129 resulted in functional receptors only when the residue could accept a hydrogen bond, but with both these and other substitutions, no [(3)H]granisetron binding could be detected, indicating a role in ligand binding. We propose that Glu129 faces into the binding pocket, where, through its ability to hydrogen bond, it plays a critical role in ligand binding. Thus, the data support a modified model of the 5-HT3 receptor binding site and show that loop A plays a critical role in both the ligand binding and function of this receptor. |
