Type XII collagen is a member of the FACIT (fibril-associated collagens with interrupted triple helices) collagen subfamily currently composed of 9 members (collagen types VII, IX, XII, XIV, XVI, XIX, XX, and XXI). Type XII collagen is a homotrimer composed of three alpha-1(XII) chains with an approximate Mr of 220 kDa. This collagen was originally found in prevalent association with type I collagen in tendons, ligaments, perichondrium, and periosteum and all dense connective tissues, but more recent studies also document association of the collagen with basement membranes. The type XII-type I collagen connection is thought to modify the interactions between collagen type I fibrils and the surrounding matrix such as to create specific macromolecular configuration of the ECM. Alternatively spliced transcript variants encoding different isoforms of the collagen have been identified. Rotary shadowing/TEM analyses shows a structure with a thin 75-nm tail, which is frequently kinked, attached through a central globule to three finger-like projections, each 60 nm long.

Type XII collagen is a member of the FACIT (fibril-associated collagens with interrupted triple helices) collagen subfamily currently composed of 9 members (collagen types VII, IX, XII, XIV, XVI, XIX, XX, and XXI). Type XII collagen is a homotrimer composed of three alpha-1(XII) chains with an approximate Mr of 220 kDa. This collagen was originally found in prevalent association with type I collagen in tendons, ligaments, perichondrium, and periosteum and all dense connective tissues, but more recent studies also document association of the collagen with basement membranes. The type XII-type I collagen connection is thought to modify the interactions between collagen type I fibrils and the surrounding matrix such as to create specific macromolecular configuration of the ECM. Alternatively spliced transcript variants encoding different isoforms of the collagen have been identified. Rotary shadowing/TEM analyses shows a structure with a thin 75-nm tail, which is frequently kinked, attached through a central globule to three finger-like projections, each 60 nm long.