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Tang H, Fu Y, Zhan S, Luo Y. αEC, the C-Terminal Extension of Fibrinogen, Has Chaperone-like Activity. Biochemistry 2009; 48:3967-76. [DOI: 10.1021/bi900015n] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Huadong Tang
- National Engineering Laboratory for Anti-tumor Protein Therapeutics
- Beijing Key Laboratory for Protein Therapeutics
- Cancer Biology Laboratory, Department of Biological Sciences and Biotechnology
| | - Yan Fu
- National Engineering Laboratory for Anti-tumor Protein Therapeutics
- Beijing Key Laboratory for Protein Therapeutics
- Cancer Biology Laboratory, Department of Biological Sciences and Biotechnology
| | - Shunli Zhan
- National Engineering Laboratory for Anti-tumor Protein Therapeutics
| | - Yongzhang Luo
- National Engineering Laboratory for Anti-tumor Protein Therapeutics
- Beijing Key Laboratory for Protein Therapeutics
- Cancer Biology Laboratory, Department of Biological Sciences and Biotechnology
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Abstract
In addition to the conventional fibrinogen with its alpha, beta, and gamma subunit chains, there is a subclass of fibrinogen molecules, accounting for one percent of the total in human adults, in which both alpha chains have been replaced by extended alpha chains (alpha E) that sport a globular C-terminal domain (alpha EC) comparable to beta C and gamma C. Using nomenclature based on molecular weight, the subclass of alpha E-containing molecules has been named fibrinogen-420 to differentiate it from the better known fibrinogen, now referred to as fibrinogen-340. Review of the events leading to the discovery of fibrinogen-420 in the early 1990s and its subsequent characterization, culminating in the crystal structure of its unique alpha EC domains, highlights special aspects of its evolutionary history, outstanding features of its structure, and the perplexities of its biology. Various working hypotheses that have driven prior investigation are evaluated and practical insights are offered to spur further research into the role of fibrinogen-420.
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Affiliation(s)
- G Grieninger
- Lindsley F. Kimball Research Institute, New York Blood Center, 310 East 67th Street, New York, New York 10021, USA.
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Abstract
Human fibrinogen-420, (Eβγ)2, was isolated from plasma and evaluated for its ability to form clots and for its susceptibility to proteolysis. Clotting parameters, including cross-linking of subunit chains, of this subclass and of the more abundant fibrinogen-340 (βγ)2, were found to be similar, suggesting little impact of the unique EC domains of fibrinogen-420 on coagulation. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) analysis of plasmic digestion patterns revealed production from fibrinogen-420 of the conventional fibrinogen degradation products, X, Y, D, and E, to be comparable to that from fibrinogen-340 in all respects except the presence of at least 2 additional cleavage products that were shown by Western blot analysis to contain the EC domain. One was a stable fragment (ECX) comigrating with a 34-kd yeast recombinant EC domain, and the other was an apparent precursor. Their release occurred early, before that of fragments D and E. Two bands of the same mobility and antibody reactivity were found in Western blots of plasma collected from patients with myocardial infarction shortly after the initiation of thrombolytic therapy.
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Abstract
AbstractHuman fibrinogen-420, (Eβγ)2, was isolated from plasma and evaluated for its ability to form clots and for its susceptibility to proteolysis. Clotting parameters, including cross-linking of subunit chains, of this subclass and of the more abundant fibrinogen-340 (βγ)2, were found to be similar, suggesting little impact of the unique EC domains of fibrinogen-420 on coagulation. Sodium dodecyl sulfate–polyacrylamide gel electrophoresis (SDS-PAGE) analysis of plasmic digestion patterns revealed production from fibrinogen-420 of the conventional fibrinogen degradation products, X, Y, D, and E, to be comparable to that from fibrinogen-340 in all respects except the presence of at least 2 additional cleavage products that were shown by Western blot analysis to contain the EC domain. One was a stable fragment (ECX) comigrating with a 34-kd yeast recombinant EC domain, and the other was an apparent precursor. Their release occurred early, before that of fragments D and E. Two bands of the same mobility and antibody reactivity were found in Western blots of plasma collected from patients with myocardial infarction shortly after the initiation of thrombolytic therapy.
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The EC Domains of Human Fibrinogen420Contain Calcium Binding Sites But Lack Polymerization Pockets. Blood 1998. [DOI: 10.1182/blood.v92.10.3669] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractThe extended (E) isoform unique to Fibrinogen420 (Fib420) is distinguished from the conventional chain of Fibrinogen340 by the presence of an additional 236-residue carboxyl terminus globular domain (EC). A recombinant form of EC (rEC), having a predicted mass of 27,653 Daltons, was expressed in yeast (Pichia pastoris) and purified by anion exchange column chromatography. Purified rEC appears to be predominantly intact, as judged by N-terminal sequence analysis, mass spectral analysis of the C-terminal cyanogen bromide (CNBr) fragment, and comparison of recognition by epitope-specific monoclonal antibodies. Carbohydrate determination, coupled with analysis of CNBr digestion fragments, confirms N-linked glycosylation at Asn667, the site at which sugar is attached in E. Analysis of CNBr digestion fragments confirms that two disulfide bridges exist at cysteine pairs E613/644 and E780/793. In the presence of 5 mmol/L EDTA, rEC is highly susceptible to plasmic degradation, but Ca2+ (5 mmol/L) renders rEC resistant. No protective effect from plasmic degradation was conferred to rEC by the peptides GPRPamide or GHRP, nor did rEC bind to a GPR peptide column. These results suggest that the EC domain contains a calcium-binding site, but lacks a polymerization pocket. By analogy with the site elucidated in the γC domain, we predict that the EC calcium binding site involves residues E772-778: DADQWEE.
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Abstract
The extended (E) isoform unique to Fibrinogen420 (Fib420) is distinguished from the conventional chain of Fibrinogen340 by the presence of an additional 236-residue carboxyl terminus globular domain (EC). A recombinant form of EC (rEC), having a predicted mass of 27,653 Daltons, was expressed in yeast (Pichia pastoris) and purified by anion exchange column chromatography. Purified rEC appears to be predominantly intact, as judged by N-terminal sequence analysis, mass spectral analysis of the C-terminal cyanogen bromide (CNBr) fragment, and comparison of recognition by epitope-specific monoclonal antibodies. Carbohydrate determination, coupled with analysis of CNBr digestion fragments, confirms N-linked glycosylation at Asn667, the site at which sugar is attached in E. Analysis of CNBr digestion fragments confirms that two disulfide bridges exist at cysteine pairs E613/644 and E780/793. In the presence of 5 mmol/L EDTA, rEC is highly susceptible to plasmic degradation, but Ca2+ (5 mmol/L) renders rEC resistant. No protective effect from plasmic degradation was conferred to rEC by the peptides GPRPamide or GHRP, nor did rEC bind to a GPR peptide column. These results suggest that the EC domain contains a calcium-binding site, but lacks a polymerization pocket. By analogy with the site elucidated in the γC domain, we predict that the EC calcium binding site involves residues E772-778: DADQWEE.
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Formation of the Human Fibrinogen Subclass Fib420: Disulfide Bonds and Glycosylation in Its Unique (EChain) Domains. Blood 1998. [DOI: 10.1182/blood.v92.9.3302] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
AbstractCOS 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.
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Formation of the Human Fibrinogen Subclass Fib420: Disulfide Bonds and Glycosylation in Its Unique (EChain) Domains. Blood 1998. [DOI: 10.1182/blood.v92.9.3302.421k48_3302_3308] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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.
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Spraggon G, Applegate D, Everse SJ, Zhang JZ, Veerapandian L, Redman C, Doolittle RF, Grieninger G. Crystal structure of a recombinant alphaEC domain from human fibrinogen-420. Proc Natl Acad Sci U S A 1998; 95:9099-104. [PMID: 9689040 PMCID: PMC21298 DOI: 10.1073/pnas.95.16.9099] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/11/1998] [Indexed: 02/08/2023] Open
Abstract
The crystal structure of a recombinant alphaEC domain from human fibrinogen-420 has been determined at a resolution of 2.1 A. The protein, which corresponds to the carboxyl domain of the alphaE chain, was expressed in and purified from Pichia pastoris cells. Felicitously, during crystallization an amino-terminal segment was removed, apparently by a contaminating protease, allowing the 201-residue remaining parent body to crystallize. An x-ray structure was determined by molecular replacement. The electron density was clearly defined, partly as a result of averaging made possible by there being eight molecules in the asymmetric unit related by noncrystallographic symmetry (P1 space group). Virtually all of an asparagine-linked sugar cluster is present. Comparison with structures of the beta- and gamma-chain carboxyl domains of human fibrinogen revealed that the binding cleft is essentially neutral and should not bind Gly-Pro-Arg or Gly-His-Arg peptides of the sort bound by those other domains. Nonetheless, the cleft is clearly evident, and the possibility of binding a carbohydrate ligand like sialic acid has been considered.
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Affiliation(s)
- G Spraggon
- Center for Molecular Genetics, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0634, USA
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