Stereoselective binding of chiral ligands to single nucleotide polymorphisms of the human organic cation transporter-1 determined using cellular membrane affinity chromatography.

Membranes from stably transfected cell lines that express two point mutations of the human organic cation transporter-1 (hOCT1), R488M and G465R, have been immobilized on the immobilized artificial membrane (IAM) liquid chromatographic stationary phase to form two cellular membrane affinity chromatography (CMAC) columns, CMAC(hOCT1(G465R)) and CMAC(hOCT1(R488M)). Columns were created using both stationary phases, and frontal displacement chromatography experiments were conducted using [(3)H] MMP(+) (1-methyl-4-phenylpyridinium) as the marker ligand and various displacers, including the single enantiomers of verapamil, fenoterol, and isoproterenol. The chromatographic data obtained were used to refine a previously developed pharmacophore for hOCT1.

Automated ligand fishing using human serum albumin-coated magnetic beads.

Human serum albumin, HSA, was immobilized onto the surface of silica-based magnetic beads. The beads were used to isolate known HSA ligands from a mixture containing ligands and nonligands. The separation was accomplished manually and was also automated. The results indicate that an automated "ligand-fishing" technique can be developed using magnetic beads containing an immobilized protein.

Pharmacophore modelling of stereoselective binding to the human organic cation transporter (hOCT1).

BACKGROUND AND PURPOSE: The human organic cation transporter-1 (hOCT1) is a polyspecific transporter that plays a role in drug distribution, metabolism and excretion. Previous studies have demonstrated that hOCT1 binding can be stereoselective, but the mechanism for stereochemical recognition has not been described. The purpose of this study was to develop a pharmacophore model to describe stereoselective binding to hOCT1. EXPERIMENTAL APPROACH: A set of 22 compounds including 8 pairs of enantiomers and five pairs of diastereomers was used to develop a pharmacophore model. The pharmacophore modeling was carried out using Catalyst version 4.11 and HypoGen and was based upon the correlation of the structures and activities (K(i) values) of the compounds used in the study. KEY RESULTS: The resulting model contained a positive ion, hydrophobic and two hydrogen-bond acceptor interaction sites. The relative enantioselectivity of 8/8 enantiomeric pairs and diastereoselectivity of 5/5 diastereomers was described by mapping to a combination of at least 3 of the 4 functional feature sites of the model. CONCLUSIONS AND IMPLICATIONS: The pharmacophore model describes stereoselective interactions with hOCT1 at one of the binding sites on the molecule.