Kinetics of Membrane Protein–Detergent Interactions Depend on Protein Electrostatics

Abstract

Interactions of a membrane protein with a detergent micelle represent a fundamental process with practical implications in structural and chemical biology. Quantitative assessment of the kinetics of protein-detergent complex (PDC) interactions has always been challenged by complicated behavior of both membrane proteins and solubilizing detergents in aqueous phase. Here, we show the kinetic reads of the desorption of maltoside-containing detergents from β-barrel membrane proteins. Using steady-state fluorescence polarization (FP) anisotropy measurements, we recorded real-time, specific signatures of the PDC interactions. The results of these measurements were used to infer the model-dependent rate constants of association and dissociation of the proteomicelles. Remarkably, the kinetics of the PDC interactions depend on the overall protein charge despite the nonionic nature of the detergent monomers. In the future, this approach might be employed for high-throughput screening of kinetic fingerprints of different membrane proteins stabilized in micelles that contain mixtures of various detergents.