1V4L

Crystal structure of a platelet agglutination factor isolated from the venom of Taiwan habu (Trimeresurus mucrosquamatus)

Summary for 1V4L

• Entry DOI: 10.2210/pdb1v4l/pdb
• Descriptor: mucrocetin alpha chain, mucrocetin beta chain (3 entities in total)
• Functional Keywords: lectin-like, square-shaped ring, blood clotting
• Biological source: Protobothrops mucrosquamatus; More
• Cellular location: Secreted: Q6TPH0 Q6TPG9
• Total number of polymer chains: 6
• Total formula weight: 90914.13

Authors

Huang, K.-F.,Ko, T.-P.,Wang, A.H.-J. (deposition date: 2003-11-14, release date: 2003-12-02, Last modification date: 2024-10-16)

Primary citation

Huang, K.F.,Ko, T.P.,Hung, C.C.,Chu, J.,Wang, A.H.,Chiou, S.H.
Crystal structure of a platelet-agglutinating factor isolated from the venom of Taiwan habu (Trimeresurus mucrosquamatus).
Biochem.J., 378:399-407, 2004

PubMed Abstract: 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.

PubMed: 14613481
DOI: 10.1042/BJ20031507

Experimental method

X-RAY DIFFRACTION (2.8 Å)