Formation of the human fibrinogen subclass fib420: disulfide bonds and glycosylation in its unique (alphaE chain) domains.
COS cell transfection has been used to monitor the assembly and secretion of fibrinogen molecules, both those of the subclass containing the novel alphaE chain and those of the more abundant subclass whose alpha chains lack alphaE's globular C-terminus. That region, referred to as the alphaEC domain, is closely related to the ends of beta and gamma chains of fibrinogen (betaC and gammaC). Transfection of COS cells with alphaE, beta, and gamma cDNAs alone results in secretion of the symmetrical molecule (alphaEbetagamma)2, also known as Fib420. Cotransfection with cDNA for the shorter alpha chain yielded secretion of both (alphabetagamma)2 and (alphaEbetagamma)2 but no mixed molecules of the structure alphaalphaE(betagamma)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 alphaE chain. No evidence from Cys --> Ser replacements was found for interchain disulfide bridges involving the four cysteines of the alphaEC domain. However, for fibrinogen secretion, the alphaE, beta, and gamma 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.
Fu
Y
Y
Lindsley F. Kimball Research Institute of the New York Blood Center, New York, NY, USA.
Zhang
J Z
JZ
Redman
C M
CM
Grieninger
G
G
D000818:Animals; D001704:Biopolymers; D019556:COS Cells; D003553:Cystine / Q000096:biosynthesis*; D018076:DNA, Complementary / Q000235:genetics; D005091:Exons / Q000235:genetics; D005340:Fibrinogen / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006031:Glycosylation; D006801:Humans; D008970:Molecular Weight; D017510:Protein Folding; D020033:Protein Isoforms / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D014162:Transfection
D001704:Biopolymers; D018076:DNA, Complementary; D020033:Protein Isoforms; D011993:Recombinant Fusion Proteins; D003553:Cystine; D005340:Fibrinogen