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

Affinity-purified antibody against human factor XII (Hageman factor) has been radiolabeled with 125I and employed as a probe to screen a human liver cDNA expression library prepared in lambda gt11. Approximately 3.5 X 10(6) recombinant phages were screened for factor XII, and two positive clones were identified and plaque purified. The largest cDNA coding for factor XII was 1571 base pairs in length and coded for amino acid residues 127-596 in the mature protein, a termination codon of TGA, a 3' noncoding sequence of 147 nucleotides, and a poly(A) tail of 11 nucleotides. The second clone contained an insert of 1334 base pairs and coded for amino acid residues 200-596. The amino acid sequence predicted by the cDNAs was in excellent agreement with that previously determined by amino acid sequence analysis. The amino acid and DNA sequences in human factor XII showed considerable homology with the corresponding domains in other serine proteases, including prothrombin, plasminogen, tissue plasminogen activator, and urokinase.