TABLE Types of Collagen, Composition, Location, and Function (Cont.)6.2 XIV [ 1(XIV)]3 Isolated from placenta; also Localized at the surface of type I detected in the bone marrow collagen fibrils along with type V and XII collagen to modulate biomechanical properties of the fibril; has a strong cell–cell binding property XV [ 1(XV)]3 Present in tissues derived from Involved in adhesion of basal lamina mesenchyme; expressed in heart to the underlying connective tissue and skeletal muscles XVI [ 1(XVI)]3 Broad tissue distribution; associated Contributes to structural with fibroblasts and arterial smooth integrity of connective tissue muscle cells, but not associated with type I collagen fibrils XVII [ 1(XVII)]3 Another unusual transmembrane collagen Interacts with integrins to stabilize found in epithelial cell membranes hemidesmosome structure XVIII [ 1(XVIII)]3 Found in epithelial and vascular Represents a basement membrane basement membrane heparan sulfate proteoglycan thought to inhibit endothelial cell proliferation and angiogenesis XIX [ 1(XIX)]3 Discovered from the sequence of Pronounced vascular and stromal human rhabdomyosarcoma cDNA; interaction suggests involvement in present in fibroblasts and liver angiogenesis XX [ 1(XX)]3 Discovered from chick embryonic Binds to the surface of other tissue; also in corneal epithelium, collagen fibrils sternal cartilage, and tendons XXI [ 1(XXI)]3 Found in human gingiva, heart and Plays a role in maintaining three-skeletal muscle, and other tissues dimensional architecture of dense containing type I collagen fibrils connective tissues XXII [α1(XXII)]3 Found in myotendinous junction, Belongs to FACIT family skeletal and heart muscle, articular Expressed at tissue junctions cartilage–synovial fluid junction, at In skin, influences epithelial-the border between hair follicle mesenchymal interactions during hair and dermis follicle morphogenesis and cycling XXIII [ 3(XXIII)]3 Discovered in metastatic tumor cells Transmembrane collagen Also expressed in heart, retina, Interacts with ECM proteins (collagen and metastatic prostate cancer cells XIII and XXV, fibronectin, heparin) Increased expression in patient with metastatic prostate cancer XXIV [ 1(XXIV)]3 Found co-expressed with type I Fibrillarlike collagen collagen in the developing bone Regarded as an ancient molecule that and eye regulates type I collagen fibrillogenesis in bone and eye during fetal development XXV [ 1(XXV)]3 A brain-specific transmembrane collagen Binds to fibrillized β-amyloid peptide Discovered in amyloid of amyloid plaques in Alzheimer’s plaques in brains of patients disease with Alzheimer’s disease Overexpressed in neurons aEach collagen molecule is composed of three polypeptide chains intertwined in a helical configuration. The Roman numerals in the parentheses in the Composition column indicate that the chains have a distinctive structure that differs from the chains with different numerals. Thus, collagen type I has two identical 1 chains and one 2 chain; collagen type II has three identical 1 chains. fibrillar collagen; FACITs; basement membrane–forming collagen; hexagonal network–forming collagen; transmembrane collagens; multiplexins Type Compositiona Location Functions