Crystal structures of fragment D from human fibrinogen and its crosslinked counterpart from fibrin

Abstract

In blood coagulation, units of the protein fibrinogen pack together to form a fibrin clot, but a crystal structure for fibrinogen is needed to understand how this is achieved. The structure of a core fragment (fragment D) from human fibrinogen has now been determined to 2.9 A resolution. The 86K three-chained structure consists of a coiled-coil region and two homologous globular entitles oriented at approximately 130 degrees to each other. Additionally, the covalently bound dimer of fragment D, known as 'double-D', was isolated from human fibrin, crystallized in the presence of a Gly-Pro-Arg-Pro-amide peptide ligand, which simulates the donor polymerization site, and its structure solved by molecular replacement with the model of fragment D.

Identification and characterization of novel mutations implicated in congenital fibrinogen disorders

“…One missense (p.Lys85X), previously reported and one novel splice‐site mutation (IVS6‐12A>G), both predicted to result in non‐functional gene products of FGG 9. Seven patients had mutations in the C‐terminus region of FGG, a mutation hotspot for variants causing dysfibrinogenemia and a region that functions in D:D interactions, which occur in amino acids 275‐300 of the FGG 6, 33. Two family members and three other unrelated patients had the previously described Bergamo II mutation ( FGG p.Arg275His) and two had a novel mutation ( FGG p.Ala289Asp) in this region 34.…”

Recombinant γT305A fibrinogen indicates severely impaired fibrin polymerization due to the aberrant function of hole ‘a’ and calcium binding sites

“…For N308K, the three hydrogen bonds between N308 and Y278 or G309 are reduced to only one hydrogen bond between K308 andY278 ( Figure 6D and E). Altogether, substitution of Ala for Thr at γ305 leads to the abolition of three hydrogen bonds inside the  module, which might induce a marked conformational change of the tertiary structure of the high affinity calcium binding site, hole 'a' and the D:D interaction site [9,10], resulting in markedly impaired fibrin polymerization compared with N308K.…”

“…These are listed on the GEHT homepage [8] (updated on 26/01/2012) (http://site.geht.org/site/Pratiques-Professionnelles/Base-de-donnees-Fibrinogene/Basede-donnees/Base-de-donnees-des-variants-du-Fibrinogene_40_.html). Crystallographic studies have provided high-resolution structures of the  module, which has several important sites relating to fibrin polymerization, including the high affinity calcium 6 binding site, hole 'a' and the D:D interaction site [9,10]. Many amino acid substitutions in the fibrinogen  module lead to reduced fibrin polymerization, namely dysfibrinogenemia [8] and some substitutions lead to impaired synthesis and/or secretion of fibrinogen in hepatocytes, namely hypofibrinogenemia caused by heterozygotes [8,11], but no substitutions lead to afibrinogenemia caused by homozygotes [8].…”

Differences in the function and secretion of congenital aberrant fibrinogenemia between heterozygous γD320G (Okayama II) and γΔN319-ΔD320 (Otsu I)

“…e l s e v i e r . c o m / l o c a t e / t h r o m r e s fibrin polymerization and the interaction site for platelet thrombus formation have been defined in the γC module; hole 'a' (Q329, D330, and D364) [4,5], high affinity calcium-binding site (D318, D320, F322, and G324) [6], D:D interaction site (γ275-300) [5], lateral aggregation sites (γ350-360 and γ370-380) [7], FXIIIa-catalyzed cross-linking site (E398 on one molecule and K406 on another molecule) [8], and platelet-binding site (the last four residues, γ408-411) [9]. Almost 300 species of genetic mutations in the fibrinogen genes, FGA, FGB, and FGG, have been associated with either the phenotype of afibrinogenemia, hypofibrinogenemia, dysfibrinogenemia, or renal amyloidosis, as listed in the fibrinogen variant data base [10], and the function and genetic and/or post-translational changes causing these phenotypes have been analyzed by molecular bases.…”