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Structure of membrane‐bound human factor Va
Author(s) -
Stoylova Svetla,
Mann Kenneth G.,
Brisson Alain
Publication year - 1994
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(94)00881-7
Subject(s) - phospholipid , factor v , crystallography , chemistry , lipid bilayer , prothrombinase , molecule , phosphatidylserine , tissue factor , serine protease , membrane , biophysics , coagulation , thrombin , protease , biochemistry , biology , platelet , surgery , organic chemistry , thrombosis , psychiatry , immunology , enzyme , medicine , psychology
Coagulation factor Va is an essential cofactor which combines with the serine protease factor Xa on a phospholipid surface to form the prothrombinase complex. In the present study, the structure of factor Va interacting with lipid surfaces containing phosphatidylserine was studied by electron microscopy. Two‐dimensional crystals of factor Va were obtained on planar lipid films under quasi‐physiological conditions. The two‐dimensional projected structure of factor Va was calculated at a resolution of 2 nm, revealing dimers of factor Va arranged on the surface lattice with the symmetry of the plane group p2. Average unit cell dimensions are a = 14.4 nm, b = 8.8 nm, γ = 107°. Each factor Va molecule presents two distinct domains of protein density consisting of one small domain, of 3 nm in diameter, connected to a larger domain of about 6 nm × 4.5 nm. The projected structure of factor Va covers an area equivalent to about fifty phospholipid molecules. In addition, edge‐on views of factor Va molecules bound to liposomes reveal a globular structure connected through a thin stem to the liposome surface. A three‐dimensional model of membrane‐bound factor Va is proposed.