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Zinc/calcium- and cadmium/cadmium-substituted concanavalin A: interplay of metal binding, pH and molecular packing
Publication Type:
Journal ArticleSource:
Volume 56, Issue Pt 12, p.1569 - 1576 (2000)URL:
PM:11092923Keywords:
Aspartic Acid; chemistry; Binding Sites; Cadmium; Calcium; Concanavalin A; Fabaceae; Histamine; Hydrogen-Ion Concentration; Models; Molecular; Plant Lectins; Plants; Medicinal; Protein Conformation; X-Ray Diffraction; ZincAbstract:
The crystal structures of cadmium/cadmium and zinc/calcium concanavalin A (con A) at pH 5.0 and pH 6.15, respectively, were determined. The structure of cadmium/cadmium con A confirms that the secondary Cd(2+)-binding site S3 is empty at pH 5. The metal-binding sites S1 and S2 are only very slightly affected by the substitution with cadmium. On the other hand, S1 and S2 and most of the protein surface of zinc/calcium con A at pH 6.15 differ from other fully metal-bound and carbohydrate-free structures. Most of these structural differences at the protein surface are a result of the interplay between metal binding, protonation and crystal packing. This interplay is expressed by relative rotations and translations of the con A units in alternative crystal packings and participation in space-group conversions inside crystals in situ. The particular crystal packing of zinc/calcium con A creates a novel zinc-binding site S4. The Zn(2+) ion in S4 ligates two aspartates from one tetramer and a histidine from a symmetry-related tetramer
Notes:
DA - 20010104
IS - 0907-4449 (Print)
LA - eng
PT - Journal Article
PT - Research Support, Non-U.S. Gov't
RN - 0 (Plant Lectins)
RN - 11028-71-0 (Concanavalin A)
RN - 51-45-6 (Histamine)
RN - 56-84-8 (Aspartic Acid)
RN - 7440-43-9 (Cadmium)
RN - 7440-66-6 (Zinc)
RN - 7440-70-2 (Calcium)
SB - IM