A novel dysfunctional protein C (protein C Padua 2) associated with a thrombotic tendency: substitution of Cys for Arg-1 results in a strongly reduced affinity for binding of Ca++.
A dysfunctional protein C (PC) molecule (Protein C Padua 2) was found in a 40-year-old man presenting with recurrent deep vein thrombosis/pulmonary embolism and a family history of thrombotic disease. The patient exhibited a normal PC antigen level, normal chromogenic activity (using Protac as PC activator) but markedly reduced coagulometric activity. After adsorption of patient plasma onto Al(OH)3, between 30% and 45% PC antigen/chromogenic activity but no coagulometric activity was detectable in the supernatant. The dysfunctional molecule exhibited reduced affinity for a Ca++ dependent anti-protein C monoclonal antibody as detected by specific ELISA assay. Immunoblotting experiments showed that PC Padua 2 had an increased MW (95 kD v 65 kD for normal PC). The lesion responsible was determined by PCR/direct sequencing to be a heterozygous CGT/TGT transition in exon 3 of the protein C gene resulting in the substitution of Arg by Cys at residue--1 in the pro-peptide leader sequence. The presence of a high MW PC was consistent with the fact that (part of) the propeptide (at least Cys-1) still was attached to the protein C molecule. This finding could also explain the strongly reduced affinity of PC Padua 2 for the Ca++ dependent anti-protein C monoclonals.
Girolami
A
A
IV Chair of Internal Medicine, University of Padua Medical School, Italy.
Simioni
P
P
Girolami
B
B
Marchiori
A
A
Millar
D S
DS
Bignell
P
P
Kakkar
V V
VV
Cooper
D N
DN
D000328:Adult; D000368:Aged; D000941:Antigens / Q000097:blood; D001120:Arginine / Q000235:genetics; D001483:Base Sequence; D002118:Calcium / Q000097:blood*; D002648:Child; D003545:Cysteine / Q000235:genetics; D006801:Humans; D015151:Immunoblotting; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009154:Mutation / Q000502:physiology*; D010375:Pedigree; D016133:Polymerase Chain Reaction; D011486:Protein C / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D011655:Pulmonary Embolism / Q000097:blood / Q000235:genetics*; D013924:Thrombophlebitis / Q000097:blood / Q000235:genetics*
D000941:Antigens; D011486:Protein C; D001120:Arginine; D003545:Cysteine; D002118:Calcium