The extracellular domain of type XVII collagen (top diagram) consists of 15 collagenous domains (solid boxes) and 16 non-collagenous domains (horizontal lines). Also shown are schematic representations of the recombinant proteins used in this study. The corresponding AA positions are indicated for the termini of each protein (from GenBank accession NM_130778). The lengths (in AA) of sec180, sec180-ΔN16, sec180-trunc and trunc-ΔN16 are 1008, 931, 331 and 254, respectively. The His-tag, when present, adds 13 AA to the length of the protein. TM, transmembrane domain; pos, position.