A; The secreted TGFBIp comprises residues 24–683. It contains an N-terminal cysteine rich domain (EMI), four fasciclin 1 domains (FAS 1–4) and a C-terminal RGD-motif. When purified from human corneas, TGFBIp has an alternative C-terminus (at residue 657) indicating a proteolytic processing of the protein, which might have a regulatory function. Mutational ‘hot spots’ are found at positions Arg124 and Arg555. B; Cartoon representation of FAS 4 from Drosophila (PDB ID: 1O70, modified from ). The FAS 4 domain consists of an N-terminal linker alpha-helix (αL), five alpha-helices (α1–5) and five beta sheets (β1–7).