Figure 4.

(A) Genomic organisation of the human factor IX gene. Exon and intron sizes are given in table 2 ▶. (B) Factor IX mRNA showing the relative size and location of the open reading frame. (C) The newly synthesised factor IX protein molecule comprising a pre- and pro-sequence (27 and 19 amino acids, respectively) and a mature peptide of 415 amino acids (total length, 461 amino acids). (D) Activated factor IX comprising an N-terminal light chain and a C-terminal heavy chain held together by a disulphide bridge between cysteine resides 132 and 279. GLA, “GLA” domain, in which 12 glutamic acid residues undergo post-translational γ-carboxylation by a vitamin K dependent carboxylase; EGF, epidermal growth factor-like domain; act, activation peptide released after proteolytic activation at arginine 145 and arginine 180; catalytic, the serine protease domain.