Gplbα Interacts Exclusively with Exosite II of Thrombin

JOURNAL OF MOLECULAR BIOLOGY

卷:426

Article

Lechtenberg, Bernhard C.¹  Freund, Stefan M. V.²  Huntington, James A.¹ 

[1] Univ Cambridge, Cambridge Inst Med Res, Dept Haematol, Cambridge CB2 0XY, England

[2] MRC, Mol Biol Lab, Cambridge CB2 0QH, England

关键词: crystallography;    exosite;    haemostasis;    NMR;    platelet;   

DOI  :  10.1016/j.jmb.2013.11.027

来源: Elsevier

【 摘 要 】

Activation of platelets by the serine protease thrombin is a critical event in haemostasis. This process involves the binding of thrombin to glycoprotein lb alpha (Gplb alpha) and cleavage of protease-activated receptors (PARs). The N-terminal extracellular domain of Gplb alpha contains an acidic peptide stretch that has been identified as the main thrombin binding site, and both anion binding exosites of thrombin have been implicated in Gplb alpha binding, but it remains unclear how they are involved. This issue is of critical importance for the mechanism of platelet activation by thrombin. If both exosites bind to Gplb alpha, thrombin could potentially act as a platelet adhesion molecule or receptor dimerisation trigger. Alternatively, if only a single site is involved, Gplb alpha may serve as a cofactor for PAR-1 activation by thrombin. To determine the involvement of thrombin's two exosites in Gplb alpha binding, we employed the complementary methods of mutational analysis, binding studies, X-ray crystallography and NMR spectroscopy. Our results indicate that the peptide corresponding to the C-terminal portion of Gplb alpha and the entire extracellular domain bind exclusively to thrombin's exosite II. The interaction of thrombin with Gplb alpha thus serves to recruit thrombin activity to the platelet surface while leaving exosite I free for PAR-1 recognition. 2013 The Authors. Published by Elsevier Ltd. All rights reserved.

【 授权许可】

Free