Molecular basis of a hereditary type I protein S deficiency caused by a substitution of Cys for Arg474.
The molecular basis for a hereditary type I protein S (PS) deficiency was investigated. DNA sequence analysis in the proband showed a novel missense mutation substituting Cys (TGT) for Arg474 (CGT) that is a highly conserved amino acid residue among the related proteins. This missense mutation cosegregated with the type I PS deficiency in this family. Transient expression studies showed that the secretion of the recombinant Cys-mutant PS was markedly decreased compared with that of the recombinant wild-type PS, reproducing the observed phenotype of type I deficiency. Stable expression and pulse-chase experiments demonstrated an intracellular degradation and an impaired secretion of the recombinant Cys-mutant PS. Furthermore, the substitution of Arg474 by Ala or Glu, but not by Lys, markedly reduced the secretion of the recombinant PS mutants in transient expression studies, suggesting that a positively charged basic amino acid might be needed at residue 474 and might play a key role in the protein structure and conformation of the sex hormone binding globulin-homology domain of the PS molecule. We postulate that the loss of the highly conserved Arg474 might be responsible for the type I PS deficiency inherited in this family.
Yamazaki
T
T
First Department of Internal Medicine, Nagoya University School of Medicine, Nagoya, Japan.
Katsumi
A
A
Kagami
K
K
Okamoto
Y
Y
Sugiura
I
I
Hamaguchi
M
M
Kojima
T
T
Takamatsu
J
J
Saito
H
H
D000727:Androgen-Binding Protein / Q000737:chemistry; D000818:Animals; D001120:Arginine; D001483:Base Sequence; D001665:Binding Sites; D016466:CHO Cells; D002417:Cattle; D002461:Cell Line, Transformed; D002522:Chlorocebus aethiops; D003241:Consanguinity; D006224:Cricetinae; D003545:Cysteine; D018076:DNA, Complementary / Q000235:genetics; D005260:Female; D020022:Genetic Predisposition to Disease; D005822:Genetic Vectors / Q000235:genetics; D006801:Humans; D007797:Laminin / Q000737:chemistry; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D017354:Point Mutation; D017293:Protein S / Q000235:genetics*; D018455:Protein S Deficiency / Q000235:genetics*; D011817:Rabbits; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013927:Thrombosis / Q000235:genetics
D000727:Androgen-Binding Protein; D018076:DNA, Complementary; D007797:Laminin; D017293:Protein S; D011993:Recombinant Fusion Proteins; D001120:Arginine; D003545:Cysteine