Several members of a family from Scranton, Pennsylvania were identified to have normal
levels of prothrombin antigen while their prothrombin clotting activity was approximately
50% of normal. There has been no previous history of bleeding or other clinical manifestations
in this family. The genomic DNA from the proband was amplified for all exons in the
prothrombin gene and analyzed by single strand conformation polymorphism (SSCP)/heteroduplex
analysis followed by DNA sequence analysis and restriction enzyme digestion. A mutation
at nucleotide 20040 in exon 14 was identified and confirmed by restriction enzyme
digestion. This mutation results in the substitution of Thr for Lys at amino acid
556. Amino acid 556 has been reported as one of the key residues for the binding of
Na+ in the thrombin portion of the protein.
Keywords
Prothrombin - dysprothrombinemia - abnormal prothrombin - Na
+ binding - SSCP/heteroduplex analysis