Human platelet fibrinogen gamma chain structure

Blood. 1984 May;63(5):990-5.

Abstract

Human plasma fibrinogen is produced by liver parenchymal cells. Such molecules contain two classes of gamma-chains (gamma A, gamma'), which differ with respect to their COOH-terminal sequences. When fibrin is crosslinked in the presence of factor XIIIa and Ca2+, three types of gamma-dimer are formed (gamma A-gamma A; gamma A-gamma'; gamma'-gamma'). A separate fibrinogen pool is located in platelet alpha-granules. We analyzed this fibrinogen to determine whether gamma'-chains were present to the same extent (7%) that they are found in plasma fibrinogen. Electrophoretic analysis (Laemmli system) of reduced samples of the clot that formed subsequent to release of fibrinogen from thrombin-stimulated washed platelets, revealed a single crosslinked gamma-dimer band in the gamma A-gamma A position. Material collected into EDTA-containing buffer and subsequently crosslinked in the presence of added factor XIII and Ca2+ also revealed a gamma A-gamma A dimer band. This finding was further investigated by Western blotting of reduced gel specimens that had been reacted with an anti-gamma-chain antibody followed by 125I-labeled protein A. A single type of gamma-chain, gamma A, was present in the fibrinogen from a Triton X-100 or 10 M urea platelet lysate, or in noncrosslinked fibrin obtained from thrombin-treated platelets. Crosslinked reduced fibrin from thrombin-treated platelets or that prepared from the Triton lysate revealed a single type of gamma-dimer, gamma A-gamma A. We conclude that there are no gamma'-chains (less than 1%) in platelet fibrinogen. This structural difference from hepatic fibrinogen probably results from differences in the processing and/or regulation of the fibrinogen gamma-chain gene in megakaryocytes.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Afibrinogenemia / blood
  • Afibrinogenemia / genetics
  • Amino Acid Sequence
  • Animals
  • Blood Platelets / analysis*
  • Chemical Phenomena
  • Chemistry
  • Cross-Linking Reagents / pharmacology
  • Electrophoresis, Polyacrylamide Gel
  • Fibrin Fibrinogen Degradation Products / metabolism
  • Fibrinogen* / genetics
  • Humans
  • Protein Conformation
  • Rabbits

Substances

  • Cross-Linking Reagents
  • Fibrin Fibrinogen Degradation Products
  • fibrinopeptides gamma
  • Fibrinogen