| First Author | Suryanarayanan A | Year | 2005 |
| Journal | Biochemistry | Volume | 44 |
| Issue | 25 | Pages | 9140-9 |
| PubMed ID | 15966738 | Mgi Jnum | J:99836 |
| Mgi Id | MGI:3584052 | Doi | 10.1021/bi050661e |
| Citation | Suryanarayanan A, et al. (2005) The loop C region of the murine 5-HT3A receptor contributes to the differential actions of 5-hydroxytryptamine and m-chlorophenylbiguanide. Biochemistry 44(25):9140-9 |
| abstractText | Sequence and predicted structural similarities between members of the Cys loop superfamily of ligand-gated ion channel receptors and the acetylcholine binding protein (AChBP) suggest that the ligand-binding site is formed by six loops that intersect at subunit interfaces. We employed site-directed mutagenesis to investigate the role of amino acids from the loop C region of the murine 5-HT(3AS)R in interacting with two structurally different agonists, serotonin (5-HT) and m-chlorophenylbiguanide (mCPBG). Mutant receptors were evaluated using radioligand binding, two-electrode voltage clamp, and immunofluorescence studies. Electrophysiological assays were employed to identify changes in response characteristics and relative efficacies of mCPBG and the partial agonist, 2-methyl 5-HT (2-Me5-HT). We have also constructed novel 5-HT and mCPBG docked models of the receptor binding site based on homology models of the AChBP. Both ligand-docked models correlate well with results from mutagenesis and electrophysiological assays. Four key amino acids were identified as being important to ligand binding and/or gating of the receptor. Among these, I228 and D229 are specific for effects mediated by 5-HT compared to mCPBG, indicating a differential interaction of these ligands with loop C. Residues F226 and Y234 are important for both 5-HT and mCPBG interactions. Mutations at F226, I228, and Y234 also altered the relative efficacies of agonists, suggesting a role in the gating mechanism. |
