Two stages of substrate discrimination dictate selectivity in the Escherichia coli MetNI-Q ABC transporter system.

ABSTRACT: The Escherichia coli MetNI-Q importer, an ATP-binding cassette (ABC) transporter, mediates the uptake of both L- and D-enantiomers of methionine. The original in vivo uptake studies show a strong preference for L-Met over D-Met, but the molecular basis of this selectivity is unclear. In this work, we systematically examine substrate discrimination by the MetNI transporter and MetQ substrate-binding protein using an array of biophysical and biochemical techniques. Based on the kinetic and thermodynamic parameters of individual intermediates in the transport cycle, we uncover multiple steps in the transport cycle that confer substrate specificity. As in many other ABC importer systems, selectivity is applied at the level of binding to the substrate-binding protein: MetQ dictates a 1000-fold

SUBMITTER: Yang JG 

PROVIDER: S-EPMC12357092 | biostudies-literature | 2025 Jul

REPOSITORIES: biostudies-literature