Crystal Structure of Prothrombin Reveals Conformational Flexibility and Mechanism of Activation

摘要: The zymogen prothrombin is composed of fragment 1 containing a Gla domain and kringle-1, 2 kringle-2, protease A B chains. prothrombinase complex assembled on the surface platelets converts to thrombin by cleaving at Arg-271 Arg-320. three-dimensional architecture molecular basis its activation remain elusive. Here we report first x-ray crystal structure as Gla-domainless construct carrying an Ala replacement catalytic Ser-525. Prothrombin features conformation 80 Å long, with positioned 36° angle relative main axis coaxial domain. High flexibility linker connecting two kringles suggests multiple arrangements for kringle-1 rest molecule. Luminescence resonance energy transfer measurements detect distinct conformations in solution, 3:2 ratio, distance between either fully extended (54 ± Å) or partially collapsed (≤34 seen structure. mechanism emerges from Of sites cleavage, located disordered region kringle-2 chain, but Arg-320 well defined within not accessible proteolysis solution. Burial prevents autoactivation directs cleave first. Reversal local electrostatic potential then redirects toward Arg-320, leading generation via prethrombin-2 intermediate.