Abstract
The sodium-galactose cotransporter from Vibrio parahaemolyticus (vSGLT) was first cloned and functionally characterized by the laboratory of Ernest M. Wright in 2000, establishing a one-to-one Na(+):sugar coupling stoichiometry and pioneering a bacterial model for human SGLTs. Here, we revisit vSGLT using solid-supported membrane electrophysiology on the Nanion SURFE(2)R N1, providing a modern, non-radioactive kinetic analysis of Na(+)-coupled sugar transport. Rapid transient currents were observed upon substrate application to proteoliposomes containing purified vSGLT. D-galactose elicited the largest Na(+)-dependent responses, followed by D-glucose and D-fucose, while no transport was observed in K(+)-based solutions. Apparent kinetic parameters recapitulate the overall trends observed in the original radiolabeled uptake assays, with K(m)(Na(+)) ≈ 18 mM and K(m)(gal) ≈ 9.8 mM. These findings validate the SURFE(2)R N1 SSM system as a quantitative, label-free method for Na(+) symport characterization and demonstrate that vSGLT retains its canonical substrate selectivity and stoichiometry.