Transient expression of FV missense mutants in COS-1 cells. Plasmids containing wild-type (pMT2/FV) or mutant (pMT2/FV-Cys472Gly and pMT2/FV-Val1813Met) FV cDNA were transiently transfected in COS-1 cells by using LIPOFECTAMINE 2000 reagent. Antigen levels of recombinant FV were measured both in conditioned media and in the corresponding cell lysates by an EIA assay 72 hours after transfection. Bars represent means ± SD of 3 independent experiments, each performed in duplicate. The mean values of wild-type FV are set as 100%; SDs of wild-type FV measurements never exceeded 10%.