6CVL

Crystal structure of the Escherichia coli ATPgS-bound MetNI methionine ABC transporter in complex with its MetQ binding protein

Summary for 6CVL

• Entry DOI: 10.2210/pdb6cvl/pdb
• Related: 3DHW 3TUI 3TUJ 3TUZ
• Descriptor: MetN nucleotide-binding subunit, MetI transmembrane subunit, MetQ periplasmic binding protein, ... (6 entities in total)
• Functional Keywords: metniq, outward-facing conformation, catalytic intermediate state, membrane protein
• Biological source: Escherichia coli (strain K12); More
• Total number of polymer chains: 5
• Total formula weight: 148444.14

Authors

Nguyen, P.T.,Kaiser, J.T.,Rees, D.C. (deposition date: 2018-03-28, release date: 2018-11-14, Last modification date: 2024-05-22)

Primary citation

Nguyen, P.T.,Lai, J.Y.,Lee, A.T.,Kaiser, J.T.,Rees, D.C.
Noncanonical role for the binding protein in substrate uptake by the MetNI methionine ATP Binding Cassette (ABC) transporter.
Proc. Natl. Acad. Sci. U.S.A., 115:E10596-E10604, 2018

PubMed Abstract: The 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 Å resolution of the ATPγS-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.

PubMed: 30352853
DOI: 10.1073/pnas.1811003115

Experimental method

X-RAY DIFFRACTION (2.953 Å)