4M64

3D crystal structure of Na+/melibiose symporter of Salmonella typhimurium

Summary for 4M64

• Entry DOI: 10.2210/pdb4m64/pdb
• Descriptor: Melibiose carrier protein (1 entity in total)
• Functional Keywords: melibiose permease, melibiose/na+ symport, membrane transport protein, membrane carrier, glycoside-pentoside-hexuronide:cation symporter family, major facilitator superfamily, secondary active transport, transport protein
• Biological source: Salmonella typhimurium
• Cellular location: Cell inner membrane; Multi-pass membrane protein: P30878
• Total number of polymer chains: 4
• Total formula weight: 216942.53

Authors

Ethayathulla, A.S.,Guan, L. (deposition date: 2013-08-08, release date: 2014-01-15, Last modification date: 2024-04-03)

Primary citation

Ethayathulla, A.S.,Yousef, M.S.,Amin, A.,Leblanc, G.,Kaback, H.R.,Guan, L.
Structure-based mechanism for Na(+)/melibiose symport by MelB.
Nat Commun, 5:3009-3009, 2014

PubMed Abstract: The bacterial melibiose permease (MelB) belongs to the glycoside-pentoside-hexuronide:cation symporter family, a part of the major facilitator superfamily (MFS). Structural information regarding glycoside-pentoside-hexuronide:cation symporter family transporters and other Na(+)-coupled permeases within MFS has been lacking, although a wealth of biochemical and biophysical data are available. Here we present the three-dimensional crystal structures of Salmonella typhimurium MelBSt in two conformations, representing an outward partially occluded and an outward inactive state of MelBSt. MelB adopts a typical MFS fold and contains a previously unidentified cation-binding motif. Three conserved acidic residues form a pyramidal-shaped cation-binding site for Na(+), Li(+) or H(+), which is in close proximity to the sugar-binding site. Both cosubstrate-binding sites are mainly contributed by the residues from the amino-terminal domain. These two structures and the functional data presented here provide mechanistic insights into Na(+)/melibiose symport. We also postulate a structural foundation for the conformational cycling necessary for transport catalysed by MFS permeases in general.

PubMed: 24389923
DOI: 10.1038/ncomms4009

Experimental method

X-RAY DIFFRACTION (3.35 Å)