Abstract
The availability of yeast surface display nanobody (Nb) libraries offers a convenient way to acquire antigen-specific nanobodies that may be useful for protein structure-function studies and/or therapeutic applications, complementary to the conventional method of acquiring nanobodies through immunization in camelids. In this study, we developed a general approach to select nanobodies for cytochrome P450 enzymes from a highly diverse yeast display library. We tested our method on three P450 enzymes including CYP102A1, neuronal nitric oxide synthase (nNOS), and the complex of CYP2B4:POR, using a novel streamlined approach where biotinylated P450s were bound to fluorescent-labeled streptavidin for Nb screening. The Nb-antigen binders were selectively enriched using magnetic-activated cell sorting (MACS) and fluorescence-activated cell sorting (FACS). After two rounds of MACS, the population of positive binders was enriched by >5-fold compared to the naïve library. The subsequent FACS selection, with a gating of 0.1%, identified 634, 270, and 215 positive binders for CYP102A1, nNOS, and CYP2B4:POR, respectively. The positive binders for CYP102A1 were further triaged based on EC(50) determined at various antigen concentrations. DNA sequencing of the top 30 binders of CYP102A1 resulted in 26 unique clones, 8 of which were selected for over-expression and characterization. They were found to inhibit CYP102A1-catalyzed oxidation of omeprazole with IC(50) values in the range of 0.16-2.8 µM. These results validate our approach and may be applied to other protein targets for the effective selection of specific nanobodies.