Purification and characterization of a major phosphatidylserine-binding phosphoprotein from human platelets

Biochem J. 1990 Aug 1;269(3):729-34. doi: 10.1042/bj2690729.

Abstract

We describe the isolation, lipid-binding properties and partial amino acid sequence of PS-p68, a novel 68 kDa phosphatidylserine-binding protein from human platelets. PS-p68 is an abundant constituent of platelets, accounting for 0.5-0.75% of total cell protein. It was purified from platelet cytosol by affinity chromatography. Amino acid sequence analysis yielded no similarity to identified proteins. In contrast with most known phospholipid-binding proteins, PS-p68 does not bind Ca2+ and does not require Ca2+ for its binding of phosphatidylserine. Phosphatidylserine binding to PS-p68 was inhibited by phosphatidic acid and by alkylphospholipids. PS-p68 was isolated as a major phosphoprotein from 32P-labelled platelets and was found to function as a protein kinase C substrate in vitro. However, treatment of intact platelets with phorbol 12-myristate 13-acetate, thrombin or carbacyclin did not increase PS-p68 phosphorylation. Platelets appear to be the only blood cells containing PS-p68, which was not detected in neutrophils, monocytes and lymphocytes.

MeSH terms

  • Amino Acid Sequence
  • Blood Platelets / analysis*
  • Blood Platelets / ultrastructure
  • Blood Proteins / isolation & purification*
  • Blood Proteins / metabolism
  • Carrier Proteins / blood*
  • Carrier Proteins / isolation & purification
  • Carrier Proteins / metabolism
  • Collodion / metabolism
  • Cytosol / analysis
  • Humans
  • Molecular Sequence Data
  • Phosphoproteins / blood
  • Phosphoproteins / isolation & purification
  • Phosphoproteins / metabolism
  • Phosphorylation
  • Protein Binding
  • Tissue Distribution

Substances

  • Blood Proteins
  • Carrier Proteins
  • Phosphoproteins
  • Collodion