title: The role of the Gla domain in the activation of bovine coagulation factor X by the snake venom protein XCP.
abstract: The activation by XCP of coagulation factor X and a factor X species lacking the Gla-domain was studied in the presence and absence of Ca2+. Both proteins could be activated at low rates in the absence of Ca2+. The activation of the unmodified factor X was stimulated by the addition of Ca2+, whereas GD factor X activation was insensitive to Ca2+. The stimulatory effect of Ca2+ seen with the unmodified factor X correlated strongly with a calcium-dependent change in intrinsic protein fluorescence. This conformational change required the Gla-domain as the fluorescence emission of GD factor X was the same with or without Ca2+. Fluorescence changes which accompanied activation were the same for both factor X and GD factor X. This suggests that the Gla-domain does not participate in the structural changes which accompany activation.
mesh_terms: D015055:1-Carboxyglutamic Acid; D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002417:Cattle; D005170:Factor X / Q000378:metabolism*; D015951:Factor Xa; D005971:Glutamates; D007700:Kinetics; D013050:Spectrometry, Fluorescence; D014757:Viper Venoms / Q000494:pharmacology*
chemical_list: D005971:Glutamates; D014757:Viper Venoms; D015055:1-Carboxyglutamic Acid; D005170:Factor X; D015951:Factor Xa; D002118:Calcium