Figure 3.

(A) Factor VIII mRNA showing the extent and location of the open reading frame. (B) The newly synthesised factor VIII protein molecule comprising a pre-sequence of 19 amino acids and a mature peptide of 2332 amino acids (total length, 2351 amino acids). A1–3, B, C1, and C2 represent domains assigned according to homologies within the protein (the boundaries are somewhat arbitrary). The arginine residues signalling the sites for proteolytic activation are arrowed. (C) Activated factor VIII comprising a heterotrimer in which the dimeric N-terminal heavy chain is held together with the monomeric C-terminal light chain by a metal ion bridge (Ca²⁺).