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Title
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A Kazal-type inhibitor with thrombin specificity from Rhodnius prolixus.
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Authors
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T.Friedrich,
B.Kröger,
S.Bialojan,
H.G.Lemaire,
H.W.Höffken,
P.Reuschenbach,
M.Otte,
J.Dodt.
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Ref.
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J Biol Chem, 1993,
268,
16216-16222.
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PubMed id
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Abstract
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A thrombin-specific inhibitor with an apparent molecular mass of 11 kDa has been
purified from the insect Rhodnius prolixus. Amino-terminal protein sequence
analysis allowed the molecular cloning of the corresponding cDNA. The open
reading frame codes for a protein of about 103 amino acid residues and displays
an internal sequence homology of residues 6-48 with residues 57-101 indicating a
two-domain structure. Based on the amino acid sequence the two domains exhibit
high homology to protease inhibitors belonging to the Kazal-type family. Model
building suggests that the first domain binds to the active site with residue
His10 pointing into the specificity pocket. From gel filtration and
tight-binding inhibition experiments the inhibitor appears to form 1:1 complexes
with thrombin. Periplasma-directed heterologous expression of the rhodniin cDNA
in Escherichia coli yields the intact thrombin inhibitor. Natural and
recombinant rhodniin both display inhibition constants of about 2 x 10(-13) M.
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