Human factor VII deficiency caused by S339C mutation located adjacent to the specificity pocket of the catalytic domain.
This report documents our identification of a novel factor VII (FVII) gene mutation in a Japanese boy with FVII deficiency. The proband's FVII activity was 34% and his FVII antigen level was 40% of normal controls. DNA sequence analysis of the proband's FVII gene identified a C to G point mutation at nucleotide position 10 933 in exon 8, which results in the substitution of Cys (TGC) for Ser339 (TCC). Hinf I digestion results indicate the proband and his mother were heterozygous for the mutation. Both wild-type and mutant FVIIs were transiently expressed in COS-1 cells. FVII levels measured in the culture medium of FVII Ser339Cys mutants were markedly reduced as compared to those of cells with FVII wild-type. The amount of intracellular FVII in FVII Ser339Cys mutants was 80% of that in wild-type. In the wild-type FVII, Ser339 is juxtaposed to Asp338, which is positioned at the bottom of the substrate-binding pocket in the protease domain and located adjacent to FVII Cys340, that forms a disulphide bond with Cys368. We suspect that the creation of a novel unpaired cysteine through this mutation leads to abnormal disulphide bonding during protein folding, thereby reducing the secretion of FVII.
Department of Medical Technology, School of Allied Medical Sciences, Shinshu University, 3-1-1 Matsumoto Asahi, 390-8621 Japan. itosamu@gipac.shinshu-u.ac.jp
Osamu
O
Takamiya
M
M
Seta
K
K
Tanaka
F
F
Ishida
D020134:Catalytic Domain / Q000235:genetics*; D002648:Child; D003001:Cloning, Molecular; D003545:Cysteine / Q000235:genetics; D004252:DNA Mutational Analysis; D005167:Factor VII / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D005168:Factor VII Deficiency / Q000235:genetics*; D006579:Heterozygote; D006801:Humans; D007564:Japan; D008297:Male; D017354:Point Mutation
D005167:Factor VII; D003545:Cysteine