Schematic representation of the human collagen XVIII variants, termed as SHORT, MIDDLE and LONG/FZ. Collagenous sequences are shown in white. Non-collagenous (NC) amino terminal sequences common to all variants are shown in black. Non-collagenous amino terminal sequences common to the two long variants are shown in grey. A non-collagenous amino terminal sequence specific to the LONG/FZ variant is marked with waves. The amino acid lengths (aa) and the predicted molecular masses (kDa) of these sequences are given, as are those of the full length type XVIII collagen molecules. Signal sequences are indicated by vertical and horizontal hatching. The epitopes of the antibodies used in this work are shown by black horizontal lines. The molecular masses of some endostatin-containing carboxy-terminal fragments are also indicated.