1dq2
Unlocked metal-free concanavalin A
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OverviewOverview
The reversible binding of manganese and calcium to concanavalin A, determines the carbohydrate binding of the lectin by inducing large, conformational changes. These changes are governed by the isomerization of, a non-proline peptide bond, Ala-207-Asp-208, positioned in a beta-strand, in between the calcium binding site S2 and the carbohydrate, specificity-determining loop. The replacement of calcium by manganese, allowed us to investigate the structures of the carbohydrate binding, locked state and the inactive, unlocked state of concanavalin A, both with, and without metal ions bound. Crystals of unlocked metal-free concanavalin, A convert to the locked form with the binding of two Mn(2+) ions. Removal, of these ions from the crystals traps metal-free concanavalin A in its, locked state, a minority species in solution. The ligation of a metal ion, in S2 to unlocked concanavalin A causes bending of the beta-strand, foregoing the S2 ligand residues Asp-10 and Tyr-12. This bending disrupts, conventional beta-sheet hydrogen bonding and forces the Thr-11 side chain, against the Ala-207-Asp-208 peptide bond. The steric strain exerted by, Thr-11 is presumed to drive the trans-to-cis isomerization. Upon, isomerization, Asp-208 flips into its carbohydrate binding position, and, the conformation of the carbohydrate specificity determining loop changes, dramatically.
About this StructureAbout this Structure
1DQ2 is a Single protein structure of sequence from Canavalia ensiformis with ACY as ligand. Full crystallographic information is available from OCA.
ReferenceReference
The structural features of concanavalin A governing non-proline peptide isomerization., Bouckaert J, Dewallef Y, Poortmans F, Wyns L, Loris R, J Biol Chem. 2000 Jun 30;275(26):19778-87. PMID:10748006
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