4m64
3D crystal structure of Na+/melibiose symporter of Salmonella typhimurium3D crystal structure of Na+/melibiose symporter of Salmonella typhimurium
Structural highlights
FunctionMELB_SALTY Responsible for melibiose transport. It is capable of using hydrogen, sodium, and lithium cations as coupling cations for cotransport, depending on the particular sugar transported (symport system). Publication Abstract from PubMedThe 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. Structure-based mechanism for Na(+)/melibiose symport by MelB.,Ethayathulla AS, Yousef MS, Amin A, Leblanc G, Kaback HR, Guan L Nat Commun. 2014 Jan 6;5:3009. doi: 10.1038/ncomms4009. PMID:24389923[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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