Dataset Information

Factor VII mutant V154G models a zymogen-like form of factor VIIa.

ABSTRACT: Proteolytic cleavage of the peptide bond between Arg(152) and Ile(153) converts the procoagulant protein Factor VII (FVII) to an activated two-chain form (FVIIa). The formation of a salt bridge between Ile(153) and Asp(343) drives the conversion of FVIIa from being zymogen-like to the active form. In the present paper, we describe the novel FVII mutant V154G (Val(154)-->Gly mutation; residue 17 in the chymotrypsin numbering system), found in three FVII-deficient patients, which models a zymogen-like form of FVIIa. Recombinant V154G FVIIa, although normally cleaved, shows markedly reduced activity towards peptidyl substrate and undetectable activity towards macromolecular substrates. Susceptibility of Ile(153) to chemical modification, in either the presence or the absence of tissue factor (TF), suggests that the reduced V154G FVIIa activity is caused by impaired salt-bridge formation, thus resulting in a zymogen-like FVIIa form. The TF-mediated protection from chemical modification of V154A indicated that Gly(154) is responsible for this peculiar feature, and suggests that this region, proximal to the heavy chain N-terminus, is directly involved in the conversion of FVII into FVIIa. V154G FVII was exploited to study the FVII-TF interaction, together with three additional FVII variants that were expressed to serve as models for different FVII forms. The comparison of binding affinities of full-length TF after relipidation in L-alpha-phosphatidylcholine for the zymogen FVII (Arg(152)-->Gln, K (d)=1.04+/-0.27 nM), inactive FVIIa (Ser(344)-->Ala, K (d)=0.27+/-0.06 nM) and a zymogen-like FVIIa (V154G, K (d)=1.15+/-0.16 nM) supports the hypothesis that preferential binding of TF to active FVIIa is insufficient to drive the 10(5)-fold enhancement of FVIIa activity. In addition, the inability of V154G FVIIa to accommodate an inhibitor in the active site, indicating an improperly shaped specificity pocket, would explain the low activity of the zymogen-like form of FVIIa, which is predominant in the absence of TF.

SUBMITTER: Toso R

PROVIDER: S-EPMC1223097 | biostudies-other | 2003 Feb

REPOSITORIES: biostudies-other

ACCESS DATA

Similar Datasets

Project description:EssentialsEssentials A fraction of coagulation factor VII circulates in blood as an activated protease (FVIIa). We evaluated FVIIa and FVIIa-antithrombin (FVIIa-AT) levels in the Cardiovascular Health Study. Polymorphisms in the F7 and PROCR loci were associated with FVIIa and FVIIa-AT levels. FVIIa may be an ischemic stroke risk factor in older adults and FVIIa-AT may assess mortality risk.SummaryBackground A fraction of coagulation factor (F) VII circulates as an active protease (FVIIa). FVIIa also circulates as an inactivated complex with antithrombin (FVIIa-AT). Objective Evaluate associations of FVIIa and FVIIa-AT with genome-wide single nucleotide polymorphisms (SNPs) and incident coronary heart disease, ischemic stroke and mortality. Patients/Methods We measured FVIIa and FVIIa-AT in 3486 Cardiovascular Health Study (CHS) participants. We performed a genome-wide association scan for FVIIa and FVIIa-AT in European-Americans (n = 2410) and examined associations of FVII phenotypes with incident cardiovascular disease. Results In European-Americans, the most significant SNP for FVIIa and FVIIa-AT was rs1755685 in the F7 promoter region on chromosome 13 (FVIIa, β = -25.9 mU mL-1 per minor allele; FVIIa-AT, β = -26.6 pm per minor allele). Phenotypes were also associated with rs867186 located in PROCR on chromosome 20 (FVIIa, β = 7.8 mU mL-1 per minor allele; FVIIa-AT, β = 9.9 per minor allele). Adjusted for risk factors, a one standard deviation higher FVIIa was associated with increased risk of ischemic stroke (hazard ratio [HR], 1.12; 95% confidence interval [CI], 1.01, 1.23). Higher FVIIa-AT was associated with mortality from all causes (HR, 1.08; 95% CI, 1.03, 1.12). Among European-American CHS participants the rs1755685 minor allele was associated with lower ischemic stroke (HR, 0.69; 95% CI, 0.54, 0.88), but this association was not replicated in a larger multi-cohort analysis. Conclusions The results support the importance of the F7 and PROCR loci in variation in circulating FVIIa and FVIIa-AT. The findings suggest FVIIa is a risk factor for ischemic stroke in older adults, whereas higher FVIIa-AT may reflect mortality risk.

Project description:BackgroundThe clotting or hemostasis system is a meticulously regulated set of enzymatic reactions that occur in the blood and culminate in formation of a fibrin clot. The precisely calibrated signaling system that prevents or initiates clotting originates with the activated Factor Seven (FVIIa) complexed with tissue factor (TF) formed in the endothelium. Here we describe a rare inherited mutation in the FVII gene which is associated with pathological clotting.Case presentationThe 52-year-old patient, with European, Cherokee and African American origins, FS was identified as having low FVII (10%) prior to elective surgery for an umbilical hernia. He was given low doses of NovoSeven (therapeutic Factor VIIa) and had no unusual bleeding or clotting during the surgery. In fact, during his entire clinical course he had no unprovoked bleeding. Bleeding instances occurred with hemostatic stresses such as gastritis, kidney calculus, orthopedic surgery, or tooth extraction, and these were handled without factor replacement. On the other hand, FS sustained two unprovoked and life-threatening instances of pulmonary emboli, although he was not treated with NovoSeven at any time close to the events. Since 2020, he has been placed on a DOAC (Direct Oral Anticoagulant, producing Factor Xa inhibition) and has sustained no further clots.Possible mechanism of (unauthorized) fvii activationFS has a congenitally mutated FVII/FVIIa gene, which carries a R315W missense mutation in one allele and a mutated start codon (ATG to ACG) in the other allele, thus rendering the patient effectively homozygous for the missense FVII. Structure based comparisons with known crystal structures of TF-VIIa indicate that the patient's missense mutation is predicted to induce a conformational shift of the C170's loop due to crowding of the bulky tryptophan to a distorted "out" position (Fig. 1). This mobile loop likely forms new interactions with activation loop 3, stabilizing a more active conformation of the FVII and FVIIa protein. The mutant form of FVIIa may be better able to interact with TF, displaying a modified serine protease active site with enhanced activity for downstream substrates such as Factor X.ConclusionsFactor VII can be considered the gatekeeper of the coagulation system. Here we describe an inherited mutation in which the gatekeeper function is altered. Instead of the expected bleeding manifestations resulting from a clotting factor deficiency, the patient FS suffered clotting episodes. The efficacy of the DOAC in treating and preventing clots in this unusual situation is due to its target site of inhibition (anti-Xa), which lies downstream of the site of action of FVIIa/TF.

Dataset Information

Factor VII mutant V154G models a zymogen-like form of factor VIIa.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets