pme568 the n terminal 800 bp 39 s of the coding region was subcloned into puc19 acc651 xba1 after introduction of an acc651 site 15 bp 39 s upstream of the initial atg by pcr of the n terminal 375 bp 39 s using the primers downstream 5 u2032 acct ggtacc ccattataagatgaaag 3 u2032 seq id no 1 acc651 upstream 5 u2032 ggtaac aagctt gagtcc 3 u2032 seq id no 2 hind3 this 375 bp 39 s acc651 hind3 fragment was ligated to the adjacent 420 bp 39 s hind3 xba1 fragment and cloned into puc19 from the resulting plasmid phw1252 the 800 bp acc651 xba1 fragment was excised and inserted with the c terminal 1750 bp xba1 snab1 fragment from pme568 into pcdna3 acc651 ecorv 5 4 kb to yield the expression plasmid phw1253 the sequence of kex2 in phw1253 is essentially as described in philippsen p et al nature 387 suppl 93 98 1997 in the yeast genome directory baby hamster kidney bhk cells expressing fvii berkner et al cold spring har bor symp quant biol 51 531 541 1986 were transfected with 2 u03bcg plasmid phw1253 as described in example 1 using lipofect amine method as described by the supplier gibco life technologies roskilde denmark stable clones were selected in medium du ibecco 39 s modified eagle 39 s medium 10 fetal calf serum 100 iu penicillin 100 iu streptomycin 1 mmol l na pyrovate and 5mg l vitamin k1 containing 1 mg l geneticin g418 gibco atter selection stable clones were picked using cloning cylinders and maintained at 37 u00b0 c in an atmosphere containing 5 co 2 stable.