Disulfide reduction abolishes tissue factor cofactor function

• Published in: Biochimica et biophysica acta Vol. 1830; no. 6; pp. 3489 - 3496
• Main Authors: Krudysz-Amblo, Jolanta, Jennings, Mark E., Knight, Tyler, Matthews, Dwight E., Mann, Kenneth G., Butenas, Saulius
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 01.06.2013
• Subjects: alkylation; Allosteric Regulation - physiology; Apoenzymes - chemistry; Apoenzymes - metabolism; binding capacity; blood coagulation; Blood Coagulation - physiology; Coenzymes - chemistry; Coenzymes - metabolism; cysteine; Disulfides; Disulfides - chemistry; Disulfides - metabolism; Extrinsic factor Xase; Factor VIIa - chemistry; Factor VIIa - metabolism; Factor X - chemistry; Factor X - metabolism; Fluorogenic assay; Humans; hydrolysis; Mass-spectrometry; Oxidation-Reduction; Pregnancy Proteins - chemistry; Pregnancy Proteins - metabolism; Protein Structure, Tertiary; Recombinant Proteins - chemistry; Recombinant Proteins - metabolism; Structure-Activity Relationship; Thromboplastin - chemistry; Thromboplastin - metabolism; Tissue factor; transmembrane proteins; PS; rTF1–263; DTT; R/A; HRP; Tissue factor; Disulfides; LPS; FVII; BSA; FX; NR/A; PCPS; PDI; Fluorogenic assay; Cys; GSH; GSSG; FXase; pTF; MS; TMB; IAA; EDTA; Mass-spectrometry; CHAPS; mAb; NR/NA; TF; FVIIa; PC; PEG; FIU; FPRnbs; R/NA; LC; Extrinsic factor Xase; Ig
• ISSN: 0304-4165; 0006-3002; 1872-8006
• DOI: 10.1016/j.bbagen.2013.02.013

Tissue factor (TF), an in vivo initiator of blood coagulation, is a transmembrane protein and has two disulfides in the extracellular domain. The integrity of one cysteine pair, Cys186–Cys209, has been hypothesized to be essential for an allosteric “decryption” phenomenon, presumably regulating TF procoagulant function, which has been the subject of a lengthy debate. The conclusions of published studies on this subject are based on indirect evidences obtained by the use of reagents with potentially oxidizing/reducing properties. The status of disulfides in recombinant TF1–263 and natural placental TF in their non-reduced native and reduced forms was determined by mass-spectrometry. Functional assays were performed to assess TF cofactor function. In native proteins, all four cysteines of the extracellular domain of TF are oxidized. Reduced TF retains factor VIIa binding capacity but completely loses the cofactor function. The reduction of TF disulfides (with or without alkylation) eliminates TF regulation of factor VIIa catalytic function in both membrane dependent FX activation and membrane independent synthetic substrate hydrolysis. Results of this study advance our knowledge on TF structure/function relationships. ► The reduction of tissue factor (TF) disulfides abolishes TF cofactor function. ► Reduced TF binds to factor VIIa but does not increase factor VIIa activity. ► Treatment of reduced TF with PDI does not restore TF function.