Deglycosylated prothrombin fragment 1. Calcium binding, phospholipid interaction, and self-assocation.
The carbohydrate portion of prothrombin fragment 1 has been removed by fluorolysis in anhydrous HF. The deglycosylated protein retains its calcium- and membrane-binding properties. The slow, calcium-dependent protein transition monitored by changes in intrinsic protein fluorescence remains intact for the aglycoprotein. Calcium-dependent protein-membrane binding is also observed and can be quantitatively reversed with EDTA. The major alteration resulting from carbohydrate removal is the degree of protein self-association. Both the normal and deglycosylated proteins undergo a rapid self-association which approaches a dimer in the presence of calcium. This self-association is independent of the slow change in intrinsic fluorescence. The deglycosylated protein then undergoes a secondary self-association with kinetics identical with the fluorescence change. This secondary self-association also occurs on the membrane surface. This suggests that the calcium-dependent conformational change exposes a site on the protein which functions in secondary self-association. The carbohydrate apparently masks this site in the native molecule.
D000596:Amino Acids / Q000032:analysis; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D002942:Circular Dichroism; D004492:Edetic Acid; D005944:Glucosamine / Q000032:analysis; D006027:Glycosides; D006801:Humans; D008027:Light; D046911:Macromolecular Substances; D008970:Molecular Weight; D010743:Phospholipids; D011485:Protein Binding; D011487:Protein Conformation; D011516:Prothrombin / Q000378:metabolism; D012542:Scattering, Radiation; D013050:Spectrometry, Fluorescence
D000596:Amino Acids; D006027:Glycosides; D046911:Macromolecular Substances; D010743:Phospholipids; D011516:Prothrombin; D004492:Edetic Acid; D005944:Glucosamine; D002118:Calcium