Crystal structures of murine thrombin in complex with the extracellular fragments of murine protease-activated receptors PAR3 and PAR4.Bah, A., Chen, Z., Bush-Pelc, L.A., Mathews, F.S., Di Cera, E.
(2007) Proc.Natl.Acad.Sci.Usa 104: 11603-11608
- PubMed: 17606903
- DOI: 10.1073/pnas.0704409104
- Primary Citation of Related Structures:
- PubMed Abstract:
- Structural Basis of Na+ Activation mimicry in murine.
Marino, F.,Chen, Z.,Ergenekan, C.E.,Bush, L.A.,Mathews, F.S.,Di Cera, E.
(2007) J.Biol.Chem. --: --
- Molecular Dissection of Na+ Binding to Thrombin.
Pineda, A.O.,Carrell, C.J.,Bush, L.A.,Prasad, S.,Caccia, S.,Chen, Z.,Mathews, F.S.,Di Cera, E.
(2004) J.Biol.Chem. 279: 31842
It has been proposed that the cleaved form of protease-activated receptor 3 (PAR3) acts as a cofactor for thrombin cleavage and activation of PAR4 on murine platelets, but the molecular basis of this physiologically important effect remains elusive. ...
It has been proposed that the cleaved form of protease-activated receptor 3 (PAR3) acts as a cofactor for thrombin cleavage and activation of PAR4 on murine platelets, but the molecular basis of this physiologically important effect remains elusive. X-ray crystal structures of murine thrombin bound to extracellular fragments of the murine receptors PAR3 ((38)SFNGGPQNTFEEFPLSDIE(56)) and PAR4 ((51)KSSDKPNPR downward arrow GYPGKFCANDSDTLELPASSQA(81), downward arrow = site of cleavage) have been solved at 2.0 and 3.5 A resolution, respectively. The cleaved form of PAR3, traced in the electron density maps from Gln-44 to Glu-56, makes extensive hydrophobic and electrostatic contacts with exosite I of thrombin through the fragment (47)FEEFPLSDIE(56). Occupancy of exosite I by PAR3 allosterically changes the conformation of the 60-loop and shifts the position of Trp-60d approximately 10 A with a resulting widening of the access to the active site. The PAR4 fragment, traced entirely in the electron density maps except for five C-terminal residues, clamps Trp-60d, Tyr-60a, and the aryl-binding site of thrombin with Pro-56 and Pro-58 at the P2 and P4 positions and engages the primary specificity pocket with Arg-59. The fragment then leaves the active site with Gly-60 and folds into a short helical turn that directs the backbone away from exosite I and over the autolysis loop. The structures demonstrate that thrombin activation of PAR4 may occur with exosite I available to bind cofactor molecules, like the cleaved form of PAR3, whose function is to promote substrate diffusion into the active site by allosterically changing the conformation of the 60-loop.
Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, Box 8231, St. Louis, MO 63110, USA.