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Title
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Crystal structure of the bovine alpha-chymotrypsin:Kunitz inhibitor complex. An example of multiple protein:protein recognition sites.
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Authors
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C.Capasso,
M.Rizzi,
E.Menegatti,
P.Ascenzi,
M.Bolognesi.
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Ref.
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J Mol Recognit, 1997,
10,
26-35.
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PubMed id
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Abstract
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The crystal structure of bovine alpha-chymotrypsin (alpha-CHT) in complex with
the bovine basic pancreatic trypsin inhibitor (BPTI) has been solved and refined
at 2.8 A resolution (R-factor = 0.18). The proteinase:inhibitor complex forms a
compact dimer (two alpha-CHT and two BPTI molecules), which may be stabilized by
surface-bound sulphate ions, in the crystalline state. Each BPTI molecule, at
opposite ends, is contacting both proteinase molecules in the dimer, through the
reactive site loop and through residues next to the inhibitor's C-terminal
region. Specific recognition between alpha-CHT and BPTI occurs at the (re)active
site interface according to structural rules inferred from the analysis of
homologous serine proteinase:inhibitor complexes. Lys15, the P1 residue of BPTI,
however, does not occupy the alpha-CHT S1 specificity pocket, being hydrogen
bonded to backbone atoms of the enzyme surface residues Gly216 and Ser217.
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