4m64

<StructureSection load='4m64' size='340' side='right' caption='[[4m64]], [[Resolution|resolution]] 3.35&Aring;' scene=''>

<table><tr><td colspan='2'>[[4m64]] is a 4 chain structure with sequence from [http://en.wikipedia.org/wiki/Salty Salty]. Full crystallographic information is available from [http://oca.weizmann.ac.il/oca-bin/ocashort?id=4M64 OCA]. For a <b>guided tour on the structure components</b> use [http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=4M64 FirstGlance]. <br>

</td></tr><tr id='gene'><td class="sblockLbl"><b>[[Gene|Gene:]]</b></td><td class="sblockDat">melB, STM4299 ([http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&srchmode=5&id=99287 SALTY])</td></tr>

<tr id='resources'><td class="sblockLbl"><b>Resources:</b></td><td class="sblockDat"><span class='plainlinks'>[http://oca.weizmann.ac.il/oca-docs/fgij/fg.htm?mol=4m64 FirstGlance], [http://oca.weizmann.ac.il/oca-bin/ocaids?id=4m64 OCA], [http://pdbe.org/4m64 PDBe], [http://www.rcsb.org/pdb/explore.do?structureId=4m64 RCSB], [http://www.ebi.ac.uk/pdbsum/4m64 PDBsum], [http://prosat.h-its.org/prosat/prosatexe?pdbcode=4m64 ProSAT]</span></td></tr>

[[http://www.uniprot.org/uniprot/MELB_SALTY MELB_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).

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.

 

== References ==

[[Category: Salty]]

[[Category: Ethayathulla, A S]]

[[Category: Guan, L]]

[[Category: Glycoside-pentoside-hexuronide:cation symporter family]]

[[Category: Transport protein]]