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. 2018 Jan 10;13(1):e0190375. doi: 10.1371/journal.pone.0190375

Fig 1. Type XVIII collagen location and structure.

Fig 1

(A) Structure of the vascular basement membrane (BM). The capillary subendothelial layer is composed of a BM and an interstitial matrix (IM). The main components of vascular basement membranes include type IV collagen, laminin and nidogen. Minor components include type XV collagen and type XVIII collagen. The components of the BM self-assemble into sheet-like structures. The BM is tightly connected to the IM through interactions between collagen type I and VI and collagen type IV and XV. (B) Isoforms of Type XVIII collagen. Collagen type XVIII exists in three isoforms, which differ in their N-terminus. The COL18A1 gene encodes these variants by the use of two promoters and alternative splicing. The short isoform has a different signal peptide from the other two, and coded by promoter 1, while the others have the same signal peptide and both coded by promoter 2. All isoforms include a thrombospondin-like domain, heparin sulphate chains and a globular C-terminal containing the type XVIII collagen fragment, endostatin.