Blood Journal
Leading the way in experimental and clinical research in hematology

Rapid purification and characterization of human platelet glycoprotein V: the amino acid sequence contains leucine-rich repetitive modules as in glycoprotein Ib

  1. T Shimomura,
  2. K Fujimura,
  3. S Maehama,
  4. M Takemoto,
  5. K Oda,
  6. T Fujimoto,
  7. R Oyama,
  8. M Suzuki,
  9. K Ichihara-Tanaka, and
  10. K Titani
  1. Department of Internal Medicine, Hiroshima University, Japan.

Abstract

Glycoprotein V (GPV) is a membrane-associated, 82 Kd platelet glycoprotein that is hydrolyzed during thrombin activation to yield 69 Kd fragment. We have developed a rapid and simple method for isolation of the protein from platelet extracts using a combination of gel permeation, anion-exchange, and lectin affinity chromatography. The partial amino acid sequence was determined by analysis of peptides generated by digestion of the S-carboxyamido-methylated protein with Achromobacter protease I or cyanogen bromide. The sequence shows a remarkable periodicity of leucine residues, which is homologous to the consensus sequence of a highly diversified protein super-family with a common repetitive module. Thrombin cleavage site was determined to be located at the C-terminal region of GPV by analysis of the products separated by sizing and reversed-phase high performance liquid chromatography. By lectin blot analysis, the existence of mucin-type carbohydrate chains was indicated, as well as the existence of asparagine-linked carbohydrate chains shown by the amino acid sequence analysis. From these data, we report a structural model of GPV that is analogous to glycoprotein Ib.