Blood, Vol. 92 No. 9 (November 1), 1998:
pp. 3302-3308
Formation of the Human Fibrinogen Subclass Fib420:
Disulfide Bonds and Glycosylation in Its Unique (
E
Chain) Domains
Yiping Fu,
Jian-Zhong Zhang,
Colvin M. Redman, and
Gerd Grieninger
From the Lindsley F. Kimball Research Institute of the New York Blood
Center, New York, NY.
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 
and 
chains of fibrinogen
(C and C). Transfection of COS cells with E, ,
and cDNAs alone results in secretion of the symmetrical molecule
(E)2, also known as
Fib420. Cotransfection with cDNA for the shorter chain
yielded secretion of both ()2 and
(E)2 but no mixed molecules of the
structure E()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, , and 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.
