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Title
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Crystal structure of the thrombin-hirudin complex: a novel mode of serine protease inhibition.
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Authors
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M.G.Grütter,
J.P.Priestle,
J.Rahuel,
H.Grossenbacher,
W.Bode,
J.Hofsteenge,
S.R.Stone.
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Ref.
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Embo J, 1990,
9,
2361-2365.
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PubMed id
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Abstract
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Thrombin is a serine protease that plays a central role in blood coagulation. It
is inhibited by hirudin, a polypeptide of 65 amino acids, through the formation
of a tight, noncovalent complex. Tetragonal crystals of the complex formed
between human alpha-thrombin and recombinant hirudin (variant 1) have been grown
and the crystal structure of this complex has been determined to a resolution of
2.95 A. This structure shows that hirudin inhibits thrombin by a previously
unobserved mechanism. In contrast to other inhibitors of serine proteases, the
specificity of hirudin is not due to interaction with the primary specificity
pocket of thrombin, but rather through binding at sites both close to and
distant from the active site. The carboxyl tail of hirudin (residues 48-65)
wraps around thrombin along the putative fibrinogen secondary binding site. This
long groove extends from the active site cleft and is flanked by the thrombin
loops 35-39 and 70-80. Hirudin makes a number of ionic and hydrophobic
interactions with thrombin in this area. Furthermore hirudin binds with its
N-terminal three residues Val, Val, Tyr to the thrombin active site cleft. Val1
occupies the position P2 and Tyr3 approximately the position P3 of the synthetic
inhibitor D-Phe-Pro-ArgCH2Cl. Thus the hirudin polypeptide chain runs in a
direction opposite to that expected for fibrinogen and that observed for the
substrate-like inhibitor D-Phe-Pro-ArgCH2Cl.
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