XXXX -independent activation of prothrombin on membranes with positively charged lipids.

@entity14942 @entity2434 @entity5597 @entity16699 @entity460 @entity1752 @entity6236
The activation of prothrombin by @entity6236 is strongly accelerated by negatively charged phospholipids plus @entity460 ions. In this paper we report that positively charged membranes can also stimulate prothrombin activation provided that the activation reaction is carried out in the absence of @entity460 ions. Membranes composed of a mixture of @entity2434 (PC) and positively charged lipids like @entity1752 , @entity5597 , or @entity14942 caused a more than 1000-fold increase of the rate of prothrombin activation. Prothrombin activation by the @entity6236 -factor Va complex was also considerably stimulated by such membranes. Stimulation of prothrombin activation by positively charged membranes was suppressed at high ionic strength. This suggests that electrostatic attraction of negatively charged proteins by positively charged membranes is the major driving force in the association of prothrombin and @entity6236 with the lipid surface. @entity460 ions strongly inhibited prothrombin activation on vesicles composed of PC and @entity1752 (80/20 M/M), which indicates that the regions of prothrombin and/or @entity6236 containing @entity16699 (gla) are important for the interaction of these proteins with positively charged membranes. The importance of the gla domain was confirmed by the observation that PC/ @entity1752 vesicles had much less effect on the reactions between proteins that lack gla residues [gla-domainless (des-1-45) prothrombin, prethrombin 1, prethrombin 2, or gla-domainless (des-1-44) @entity6236 ]. The efficiency of prothrombin and prothrombin derivatives to act as substrate decreased in the order prothrombin greater than des-1-45-prothrombin = prethrombin 1 greater than prethrombin 2, while prothrombin activation by gla-domainless (des-1-44) @entity6236 was hardly stimulated by positively charged membranes.(ABSTRACT TRUNCATED AT 250 WORDS)
