Characterization of a cDNA coding for human factor XII (Hageman factor)

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• Human factor XII (Hageman factor) is a key protein in the intrinsic pathway of blood coagulation.
• Understanding the genetic basis of factor XII is crucial for studying hemostasis and related disorders.

Purpose of the Study:

• To isolate and characterize cDNA clones encoding human factor XII.
• To determine the nucleotide and amino acid sequences of human factor XII.
• To investigate the evolutionary relationship of factor XII with other serine proteases.

Main Methods:

• Screening of a human liver cDNA expression library in lambda gt11 using a radiolabeled antibody against human factor XII.
• Identification and plaque purification of positive recombinant phages.
• DNA sequencing of cDNA inserts and amino acid sequence prediction.
• Comparison of human factor XII sequences with other serine proteases.

Main Results:

• Two positive cDNA clones for human factor XII were identified from approximately 3.5 x 10^6 recombinant phages.
• The largest cDNA insert was 1571 base pairs, coding for amino acid residues 127-596, a termination codon, and a 3' noncoding sequence with a poly(A) tail.
• The second clone contained a 1334 base pair insert, coding for residues 200-596.
• Predicted amino acid sequences closely matched previously determined sequences.
• Significant homology was observed between human factor XII sequences and domains of other serine proteases (prothrombin, plasminogen, tPA, urokinase).

Conclusions:

• The study successfully isolated and characterized human factor XII cDNA, providing valuable genetic information.
• The findings confirm the predicted amino acid sequence and reveal extensive homology with other serine proteases, shedding light on their evolutionary relationships.
• This research contributes to a deeper understanding of the factor XII gene and its role in the coagulation cascade.