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3bx4
From Proteopedia
Crystal structure of the snake venom toxin aggretin
Structural highlights
Function[AGGB_CALRH] Elicits platelet aggregation by the binding to the C-type lectin domain family 1 member B (CLEC1B/CLEC2). Binding leads to tyrosine phosphorylation in the cytoplasmic tail of CLEC1B, which promotes the binding of spleen tyrosine kinase (Syk), subsequent activation of PLCgamma2, and platelet activation and aggregation. Binding to GPIbalpha (GP1BA) and alpha2/beta-1 (ITGA2/ITGB1) may also induce aggregation, but this is controversial.[1] [2] [3] [4] [5] [6] [7] [8] 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 PubMedAggretin is a C-type lectin purified from Calloselasma rhodostoma snake venom. It is a potent activator of platelets, resulting in a collagen-like response by binding and clustering platelet receptor CLEC-2. We present here the crystal structure of aggretin at 1.7 A which reveals a unique tetrameric quaternary structure. The two alphabeta heterodimers are arranged through 2-fold rotational symmetry, resulting in an antiparallel side-by-side arrangement. Aggretin thus presents two ligand binding sites on one surface and can therefore cluster ligands in a manner reminiscent of convulxin and flavocetin. To examine the molecular basis of the interaction with CLEC-2, we used a molecular modeling approach of docking the aggretin alphabeta structure with the CLEC-2 N-terminal domain (CLEC-2N). This model positions the CLEC-2N structure face down in the "saddle"-shaped binding site which lies between the aggretin alpha and beta lectin-like domains. A 2-fold rotation of this complex to generate the aggretin tetramer reveals dimer contacts for CLEC-2N which bring the N- and C-termini into the proximity of each other, and a series of contacts involving two interlocking beta-strands close to the N-terminus are described. A comparison with homologous lectin-like domains from the immunoreceptor family reveals a similar but not identical dimerization mode, suggesting this structure may represent the clustered form of CLEC-2 capable of signaling across the platelet membrane. The crystal structure of the platelet activator aggretin reveals a novel (alphabeta)2 dimeric structure.,Hooley E, Papagrigoriou E, Navdaev A, Pandey AV, Clemetson JM, Clemetson KJ, Emsley J Biochemistry. 2008 Jul 29;47(30):7831-7. Epub 2008 Jul 3. PMID:18597489[9] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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