Blood Journal
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Formation of the Human Fibrinogen Subclass Fib420: Disulfide Bonds and Glycosylation in Its Unique (EChain) Domains

  1. Yiping Fu,
  2. Jian-Zhong Zhang,
  3. Colvin M. Redman, and
  4. Gerd Grieninger
  1. 1 From the Lindsley F. Kimball Research Institute of the New York Blood Center, New York, NY.

Abstract

COS cell transfection has been used to monitor the assembly and secretion of fibrinogen molecules, both those of the subclass containing the novel E chain and those of the more abundant subclass whose  chains lack E’s globular C-terminus. That region, referred to as the EC domain, is closely related to the ends of β and γ chains of fibrinogen (βC and γC). Transfection of COS cells with E, β, and γ cDNAs alone results in secretion of the symmetrical molecule (Eβγ)2, also known as Fib420. Cotransfection with cDNA for the shorter  chain yielded secretion of both (βγ)2 and (Eβγ)2 but no mixed molecules of the structure E(βγ)2. Exploiting the COS cells’ fidelity with regard to Fib420 production, identification was made of the highly conserved Asn667 as the sole site of N-linked glycosylation in the E chain. No evidence from Cys → Ser replacements was found for interchain disulfide bridges involving the four cysteines of the EC domain. However, for fibrinogen secretion, the E, β, and γ subunits do exhibit different requirements for integrity of the two intradomain disulfide bridges located at homologous positions in their respective C-termini, indicating dissimilar structural roles in the process of fibrinogen assembly.

© 1998 by The American Society of Hematology.

  • Submitted April 28, 1998.
  • Accepted July 6, 1998.
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