Todd T Talley1, Janet Bobango1, Martina Wilson1, Valery Fokin2, K Barry Sharpless2, Palmer Taylor3
1 Department of Biomedical and Pharmaceutical Sciences, Idaho State University College of Pharmacy, Meridian, ID
2 Skaggs School of Pharmacy & Pharmaceutical Sciences, University of California, San Diego, La Jolla, CA
3 Department of Chemistry, The Scripps Research Institute, La Jolla, CA
Many potential therapeutics fail to make it to the clinic due to undesirable side effects caused by off-target interactions. This is particularly true for nicotinic acetylcholine receptors (nAChRs), a class of pentameric ligand-gated ion channels. The nAChR subtypes share considerable structural and sequence identity with each other and with related receptors. To address this difficulty we have utilized the acetylcholine binding proteins (AChBPs) as surrogates of the receptor ligand binding domain (LBD). We have demonstrated these soluble pentameric proteins share considerable homology with human nAChRs and present a ligand binding profile similar to that observed for wild type receptors. Further, we have shown that the proteins are amenable to high throughput compound screening and have generated a large library of X-ray crystal structures of the AChBPs in complex with a wide array of natural products and ligands. The AChBPs have also been used to template the formation of novel ligands within the LDB using freeze frame in situ click chemistry. In our current endeavors we are improving the utility of the AChBPs by replacing key residues of the LBD with those found in native nAChRs subtypes generating chimeric entities with greater structural and pharmacological similarity. While this work is in its preliminary stages we have had some substantial success in replacing loop C of the AChBP with the sequence of each of the human α and β subtypes we have begun modifying other regions of the LBD. These new constructs have already provided a new array of structures affording a molecular view of the determinants of ligand recognition and providing more clinically relevant templates for click chemistry.
College of Pharmacy: Pharmaceutical Sceinces