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PDBsum entry 1v4l
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Blood clotting
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PDB id
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1v4l
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Contents |
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* Residue conservation analysis
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References listed in PDB file
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Key reference
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Title
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Crystal structure of a platelet-Agglutinating factor isolated from the venom of taiwan habu (trimeresurus mucrosquamatus).
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Authors
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K.F.Huang,
T.P.Ko,
C.C.Hung,
J.Chu,
A.H.Wang,
S.H.Chiou.
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Ref.
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Biochem J, 2004,
378,
399-407.
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PubMed id
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Abstract
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Platelet glycoprotein Ib (GPIb)-binding proteins (GPIb-BPs) from snake venoms
are usually C-type lectins, which target specific sites of GPIbalpha and elicit
distinct effects on platelets. In the present paper, we report a tetrameric
platelet-agglutinating factor (molecular mass 121.1 kDa), termed mucrocetin,
purified from the venom of Taiwan habu (Trimeresurus mucrosquamatus ).
Mucrocetin is a GPIbalpha agonist with a binding site distinct from that of
flavocetin-A (a snake venom GPIbalpha antagonist) on GPIbalpha, in spite of the
high sequence identity (94.6%) between the two venom lectins. The crystal
structure of mucrocetin was solved and refined to 2.8 A (1 A=0.1 nm) resolution,
which shows an interesting crystal packing of six-layer cylinders of
doughnut-shaped molecules. The four alphabeta heterodimers are arranged in an
unusual square-shaped ring stabilized by four interdimer 'head-to-tail'
disulphide bridges. Detailed structural comparison between mucrocetin and
flavocetin-A suggests that their disparate platelet effects are probably
attributable to different charge distributions on the putative concave binding
surface. A unique positively charged patch on the binding surface of mucrocetin,
formed by Lys102, Lys108, Lys109 and Arg123 in the alpha-subunit coupled with
Lys22, Lys102, Lys116 and Arg117 in the beta-subunit, appears to be the primary
determinant of its platelet-agglutinating activity. Conceivably, this
interesting venom factor may provide a useful tool to study platelet
agglutination by binding to the GPIb-IX-V complex.
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