期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 104, 期 28, 页码 11603-11608出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0704409104
关键词
signal transduction; x-ray structure; allostery
资金
- NHLBI NIH HHS [R01 HL058141, R29 HL049413, R01 HL049413, HL49413, HL73813, HL58141, R01 HL073813] Funding Source: Medline
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 ((KSSDKPNPR)-K-51 down arrow GYPGKFCANDSDTLELPASSQA(81), down arrow = site of cleavage) have been solved at 2.0 and 3.5 angstrom 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 (FEEFPLSDIE56)-F-47. Occupancy of exosite I by PAR3 allosterically changes the conformation of the 60-loop and shifts the position of Trp-60d approximate to 10 angstrom 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.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据