PMID: 8033893

 

    Legend: Sugar

Title : Rat platelets contain glycosylated and non-glycosylated forms of platelet factor 4

Abstract :

1. Identification and characterization by mass spectrometry
2. Platelet factor 4 is a heparin-binding protein released from the alpha granules of activated platelets
3. This study describes the purification and identification of two forms of rat platelet factor 4 , the previously characterized non-glycosylated form of 7 kDa and an additional glycosylated form of molecular mass 9 kDa
4. The two proteins both neutralized the antithrombin-III-dependent inhibitory activity of heparin
5. Although their amino acid com position was found to be the same, in the N-terminal sequence of the 9-kDa protein , the second threonine residue could not be detected and a difference of 976Da was determined by mass spectrometry
6. After digestion with O-glycanase and sialidase , the two proteins showed the same molecular mass
7. Overall consideration of these data led to identification of the higher-molecular-mass protein as a glycosylated form of rat platelet factor 4 with O-glycosylation at the second N-terminal amino acid, while the structure of the oligosaccharide core was established by mass spectrometry and sugar differentiation with lectins
8. The two forms of platelet factor 4 are both present in platelets and secreted after platelet activation