Protein C Osaka 10 with aberrant propeptide processing: loss of anticoagulant activity due to an amino acid substitution in the protein C precursor.
We studied the molecular basis of protein C deficiency in a family with a history of thromboembolic disease. An approximately 50% reduction in anticoagulant activity despite normal levels of protein C amidolytic activity and antigen was detected in plasma from the proband. All the exons and intron/exon junctions of the protein C gene were studied using a strategy that combined polymerase chain reaction amplification with DNA sequencing of the amplified fragments. We identified a C-to-A change at nucleotide number 1387 of the protein C gene in the proband and his mother, and this mutant was designated protein C Osaka 10. The C-to-A change resulted in the substitution of Ser for Arg at position -1, which is the processing protease cleavage site. The mutant protein C was partially purified from plasma of the patient's mother using barium adsorption followed by ion-exchange column chromatography. It eluted at the same sodium chloride concentration as normal protein C, and thus gamma-carboxylation of the mutant protein appeared to be normal. The apparent molecular weight of this mutant protein C was the same as that of the normal protein on immunoblotting. Amino-terminal sequence analysis showed that the light chain of the mutant protein C had an additional Ser at position-1. Thus, the loss of anticoagulant activity of protein C Osaka 10 can be explained by alteration of the conformation of the Gla domain by the additional Ser in the mutant molecule.
Miyata
T
T
Research Institute, National Cardiovascular Center, Fujishirodai, Japan.
Zheng
Y Z
YZ
Sakata
T
T
Kato
H
H
D000328:Adult; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000235:genetics; D001483:Base Sequence; D001777:Blood Coagulation / Q000235:genetics; D005260:Female; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D017354:Point Mutation; D011486:Protein C / Q000235:genetics*; D020151:Protein C Deficiency; D011498:Protein Precursors / Q000235:genetics; D011499:Protein Processing, Post-Translational / Q000235:genetics; D016415:Sequence Alignment; D013923:Thromboembolism / Q000235:genetics* / Q000378:metabolism
D000596:Amino Acids; D011486:Protein C; D011498:Protein Precursors