Isolation of an inhibitor selective for collagen-stimulated platelet aggregation from the soft tick Ornithodoros moubata

J Biol Chem. 1993 Mar 15;268(8):5445-9.

Abstract

Soluble extracts from the soft tick Ornithodoros moubata were found to inhibit collagen-, ADP-, and thrombin-stimulated platelet aggregation. One inhibitory component was purified to homogeneity by a combination of gel filtration, ion-exchange, and reverse phase high pressure liquid chromatography. The purified activity, named moubatin, is a protein of molecular weight 17,000 and it inhibits the aggregation of washed human platelets stimulated by collagen with an IC50 of approximately 50 nM in the standard assay. At a concentration of moubatin that maximally inhibited collagen-stimulated platelet aggregation, no inhibition of aggregation initiated by other effectors, including arachidonic acid, thrombin, ristocetin, and the calcium ionophore A23187, was observed. Moubatin also inhibits collagen-dependent aggregation in plasma. At a higher concentration of moubatin (> 1 microM) it was also possible to demonstrate an inhibitory effect on the final extent of aggregation induced by a low concentration of ADP. Although moubatin selectively inhibits platelet activation by collagen, it has only a minimal effect on the adhesion of platelets to collagen. The amino acid sequences of peptides derived from proteolytic cleavage of moubatin suggest that moubatin is a unique protein, consistent with its novel functional activity.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Chromatography, Gel
  • Chromatography, High Pressure Liquid
  • Chromatography, Ion Exchange
  • Collagen / pharmacology*
  • Electrophoresis, Polyacrylamide Gel
  • Humans
  • In Vitro Techniques
  • Molecular Sequence Data
  • Peptide Fragments / chemistry
  • Platelet Aggregation / drug effects*
  • Platelet Aggregation Inhibitors / isolation & purification*
  • Platelet Aggregation Inhibitors / pharmacology
  • Proteins / isolation & purification*
  • Proteins / pharmacology
  • Ticks / chemistry*

Substances

  • Peptide Fragments
  • Platelet Aggregation Inhibitors
  • Proteins
  • moubatin
  • Collagen