CHARACTERIZATION OF A FACTOR-VII MOLECULE CARRYING A MUTATION IN THE 2ND EPIDERMAL GROWTH FACTOR-LIKE DOMAIN

A missense mutation at codon 100 in the second epidermal growth factor -like domain, resulting in Gln100-->Arg, was detected in 19 out of 21 available severely factor VII (FVII) deficient patients in Norway. Sev enteen patients were homozygous, and the two remaining were compound h eterozygotes, In the homozygous patients, FVII antigen was measured to 10-28%, and activity to 0.6-6.5% of that in normal pooled plasma. Rec ombinant FVII containing the mutation was expressed transiently in CHO cells to a mean antigen level of 57% of the wild type FVII protein, a nd with a specific activity of 6% of wild type. The mutant protein had a 14-fold reduction in affinity for tissue factor (TF), whereas bindi ng of FX seemed unaffected. In line with the experimental data, molecu lar modelling of the mutation based on the coordinates of the tissue f actor/FVIIa complex showed that substituting arginine for glutamine di srupts the interface between the catalytic and second epidermal growth factor-like domains.