6cvl | pdb_00006cvl
Crystal structure of the Escherichia coli ATPgS-bound MetNI methionine ABC transporter in complex with its MetQ binding protein
Structural highlights
Function[METN_ECOLI] Part of the ABC transporter complex MetNIQ involved in methionine import. Responsible for energy coupling to the transport system (Probable). It has also been shown to be involved in formyl-L-methionine transport.[1] [2] [METQ_ECOLI] This protein is a component of a D-methionine permease, a binding protein-dependent, ATP-driven transport system.[3] [METI_ECOLI] Part of the binding-protein-dependent transport system for D-methionine and the toxic methionine analog alpha-methyl-methionine. Probably responsible for the translocation of the substrate across the membrane. Publication Abstract from PubMedThe Escherichia coli methionine ABC transporter MetNI exhibits both high-affinity transport toward l-methionine and broad specificity toward methionine derivatives, including d-methionine. In this work, we characterize the transport of d-methionine derivatives by the MetNI transporter. Unexpectedly, the N229A substrate-binding deficient variant of the cognate binding protein MetQ was found to support high MetNI transport activity toward d-selenomethionine. We determined the crystal structure at 2.95 A resolution of the ATPgammaS-bound MetNIQ complex in the outward-facing conformation with the N229A apo MetQ variant. This structure revealed conformational changes in MetQ providing substrate access through the binding protein to the transmembrane translocation pathway. MetQ likely mediates uptake of methionine derivatives through two mechanisms: in the methionine-bound form delivering substrate from the periplasm to the transporter (the canonical mechanism) and in the apo form by facilitating ligand binding when complexed to the transporter (the noncanonical mechanism). This dual role for substrate-binding proteins is proposed to provide a kinetic strategy for ABC transporters to transport both high- and low-affinity substrates present in a physiological concentration range. Noncanonical role for the binding protein in substrate uptake by the MetNI methionine ATP Binding Cassette (ABC) transporter.,Nguyen PT, Lai JY, Lee AT, Kaiser JT, Rees DC Proc Natl Acad Sci U S A. 2018 Nov 6;115(45):E10596-E10604. doi:, 10.1073/pnas.1811003115. Epub 2018 Oct 23. PMID:30352853[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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