Carbohydrate binding sites in a pancreatic α‐amylase‐substrate complex, derived from X‐ray structure analysis at 2.1 Å resolution

Protein Science - Tập 4 Số 4 - Trang 747-755 - 1995
Minxie Qian1, Richard Haser1, F. Payan1
1LCCMB-CNRS, URA 1296 Université Aix-Marseille II, Faculté de Médecine Nord Bd Pierre Dramard, 13916 Marseille Cedex 20, France

Tóm tắt

AbstractThe X‐ray structure analysis of a crystal of pig pancreatic α‐amylase (PPA, EC 3.2.1.1.) that was soaked with the substrate maltopentaose showed electron density corresponding to two independent carbohydrate recognition sites on the surface of the molecule. Both binding sites are distinct from the active site described in detail in our previous high‐resolution study of a complex between PPA and a carbohydrate inhibitor (Qian M, Buisson G, Duée E, Haser H, Payan F, 1994, Biochemistry 55:6284–6294). One of the binding sites previously identified in a 5‐Å‐resolution electron density map, lies at a distance of 20 A from the active site cleft and can accommodate two glucose units. The second affinity site for sugar units is located close to the calcium binding site. The crystal structure of the maltopentaose complex was refined at 2.1 A resolution, to an R‐factor of 17.5%, with an RMS deviation in bond distances of 0.007 Å. The model includes all 496 residues of the enzyme, 1 calcium ion, 1 chloride ion, 425 water molecules, and 3 bound sugar rings. The binding sites are characterized and described in detail. The present complex structure provides the evidence of an increased stability of the structure upon interaction with the substrate and allows identification of an N‐terminal pyrrolidonecarboxylic acid in PPA.

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Protein Science

Tập 4 Số 4

747-755

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