1ltt

LACTOSE BINDING TO HEAT-LABILE ENTEROTOXIN REVEALED BY X-RAY CRYSTALLOGRAPHY

spinqualitylabelsall models 1ltt, resolution 2.30Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 1ltt is a 7 chain structure with sequence from Escherichia coli. The September 2005 RCSB PDB Molecule of the Month feature on Cholera Toxin by David S. Goodsell is 10.2210/rcsb_pdb/mom_2005_9. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Method: X-ray diffraction, Resolution 2.3Å Ligands: BGC, GAL Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Function ELBP_ECOLX The biological activity of the toxin is produced by the A chain, which activates intracellular adenyl cyclase. Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMed Recognition of the oligosaccharide portion of ganglioside GM1 in membranes of target cells by the heat-labile enterotoxin from Escherichia coli is the crucial first step in its pathogenesis, as it is for the closely related cholera toxin. These toxins have five B subunits, which are essential for GM1 binding, and a single A subunit, which needs to be nicked by proteolysis and reduced, yielding an A1-'enzyme' and an A2-'linker' peptide. A1 is translocated across the membrane of intestinal epithelial cells, possibly after endocytosis, upon which it ADP-ribosylates the G protein Gs alpha. The mechanism of binding and translocation of these toxins has been extensively investigated, but how the protein is orientated on binding is still not clear. Knowing the precise arrangement of the ganglioside binding sites of the toxins will be useful for designing drugs against the diarrhoeal diseases caused by organisms secreting these toxins and in the development of oral vaccines against them. We present here the three-dimensional structure of the E. coli heat-labile enterotoxin complexed with lactose. This reveals the location of the binding site of the terminal galactose of GM1, which is consistent with toxin binding to the target cell with its A1 fragment pointing away from the membrane. A small helix is identified at the carboxy terminus of A2 which emerges through the central pore of the B subunits and probably comes into contact with the membrane upon binding, whereas the A1 subunit is flexible with respect to the B pentamer. Lactose binding to heat-labile enterotoxin revealed by X-ray crystallography.,Sixma TK, Pronk SE, Kalk KH, van Zanten BA, Berghuis AM, Hol WG Nature. 1992 Feb 6;355(6360):561-4. PMID:1741035 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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