The Type of Collagen
2015-07-25
Collagen is a group of naturally occurring proteins. In nature, it is found exclusively in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content. Collagen, in the form of elongated fibrils, is mostly found in fibrous tissues such as tendon, ligament and skin, and is also abundant in cornea, cartilage, bone, blood vessels, the gut, and intervertebral disc. In muscle tissue it serves as a major component of endomysium. Collagen constitutes 1% to 2% of muscle tissue, and accounts for 6% of the weight of strong, tendinous muscles. Gelatin, which is used in food and industry, is collagen that has been irreversibly hydrolyzed. Collagen is one of the long, fibrous structural proteins whose functions are quite different from those of globular proteins such as enzymes.
Collagen type I(COL1) is the most abundant collagen of the human body. It is present in scar tissue, the end product when tissue heals by repair. It is found in tendons, skin, artery walls, the endomysium of myofibrils, fibrocartilage, and the organic part of bones and teeth.
Type-II collagen is the basis for articular cartilage and hyaline cartilage.It makes up 50% of all protein in cartilage and 85-90% of collagen of articular cartilage.Type II collagen does form fibers. This fibrillar network of collagen allows cartilage to entrap the proteoglycan aggregate as well as provide tensile strength to the tissue. Type II collagen, which adds structure and strength to connective tissues, is found primarily in cartilage, the jelly-like substance that fills the eyeball (the vitreous), the inner ear, and the center portion of the discs between the vertebrae in the spine (nucleus pulposus). Three pro-alpha1(II) chains twist together to form a triple-stranded, ropelike procollagen molecule. These procollagen molecules must be processed by enzymes in the cell. Once these molecules are processed, they leave the cell and arrange themselves into long, thin fibrils that cross-link to one another in the spaces around cells.
Type III collagen is a fibrillar forming collagen comprising three alpha1(III) chains and is expressed in early embryos and throughout embryogenesis. In the adult, type III collagen is a major component of the extracellular matrix in a variety of internal organs and skin. Mutations in the COL3A1 gene have been implicated as a cause of type IV Ehlers-Danlos syndrome, a disease leading to aortic rupture in early adult life. The mutated allele was transmitted through the mouse germ line and homozygous mutant animals were derived from heterozygous intercrosses. About 10% of the homozygous mutant animals survived to adulthood but have a much shorter life span compared with wild-type mice. The major cause of death of mutant mice was rupture of the major blood vessels, similar to patients with type IV Ehlers-Danlos syndrome. Type III collagen is essential for normal collagen I fibrillogenesis in the cardiovascular system and other organs.
Type-IV collagen is a type of collagen found primarily in the basal lamina. The C-terminus domain is not removed in post-translational processing, and the fibers link head-to-head, rather than in parallel. Also, type-IV lacks the regular glycine in every third residue necessary for the tight, collagen helix. This makes the overall arrangement more sloppy with kinks. These two features cause the collagen to form in a sheet, the form of the basal lamina.
All of the type IV collagen in mammals is derived from six genetically distinct a-chain polypeptides (a1–a6). The type IV collagen a-chains have similar domain structures and share between 50–70% homology at the amino-acid level. The a-chains can be separated into three domains: an amino-terminal 7S domain, a middle triple-helical domain, and a carboxy-terminal globular non-collagenous (NC)-1 domain (see figure).
Type-V collagen is a form of fibrillar collagen associated with classical Ehlers-Danlos syndrome.Type V collagen is found in tissues containing type I collagen and appears to regulate the assembly of heterotypic fibers composed of both type I and type V collagen. This gene product is closely related to type XI collagen and it is possible that the collagen chains of types V and XI constitute a single collagen type with tissue-specific chain combinations. Collagen type V is highly expressed during tissue development and wound repair, but its exact function remains unclear. Cell binding to collagen V affects various basic cell functions and increased collagen V levels alter the structural organization and the stiffness of the ECM. Collagen V plays an essential role in modifying cell behavior during development and remodeling, when very soft tissues are present.
gen VI is a form of collagen primarily associated with the extracellular matrix of skeletal muscle.It is associated with the genes COL6A1, COL6A2, and COL6A3.Defects are associated with Bethlem myopathy and Ullrich congenital muscular dystrophy.
Collagen VI is a major structural component of microfibrils. The basic structural unit of collagen VI is a heterotrimer of the alpha1(VI), alpha2(VI), and alpha3(VI) chains. The alpha2(VI) and alpha3(VI) chains are encoded by the COL6A2 and COL6A3 genes, respectively. The protein encoded by this gene is the alpha 1 subunit of type VI collagen (alpha1(VI) chain). Mutations in the genes that code for the collagen VI subunits result in the autosomal dominant disorder, Bethlem myopathy.
Collagen, type VII, alpha 1 encodes the alpha chain of type VII collagen. The type VII collagen fibril, composed of three identical alpha collagen chains, is restricted to the basement zone beneath stratified squamous epithelia. It functions as an anchoring fibril between the external epithelia and the underlying stroma.
Mutations in this gene are associated with all forms of dystrophic epidermolysis bullosa. In the absence of mutations, however, an autoimmune response against type VII collagen can result in an acquired form of this disease called epidermolysis bullosa acquisita.Type VII collagen is also found in the retina; its function in this organ is unknown.COL7A1 is located on the short arm of human chromosome 3, in the chromosomal region denoted 3p21.31.
Collagen type I(COL1) is the most abundant collagen of the human body. It is present in scar tissue, the end product when tissue heals by repair. It is found in tendons, skin, artery walls, the endomysium of myofibrils, fibrocartilage, and the organic part of bones and teeth.
Type-II collagen is the basis for articular cartilage and hyaline cartilage.It makes up 50% of all protein in cartilage and 85-90% of collagen of articular cartilage.Type II collagen does form fibers. This fibrillar network of collagen allows cartilage to entrap the proteoglycan aggregate as well as provide tensile strength to the tissue. Type II collagen, which adds structure and strength to connective tissues, is found primarily in cartilage, the jelly-like substance that fills the eyeball (the vitreous), the inner ear, and the center portion of the discs between the vertebrae in the spine (nucleus pulposus). Three pro-alpha1(II) chains twist together to form a triple-stranded, ropelike procollagen molecule. These procollagen molecules must be processed by enzymes in the cell. Once these molecules are processed, they leave the cell and arrange themselves into long, thin fibrils that cross-link to one another in the spaces around cells.
Type III collagen is a fibrillar forming collagen comprising three alpha1(III) chains and is expressed in early embryos and throughout embryogenesis. In the adult, type III collagen is a major component of the extracellular matrix in a variety of internal organs and skin. Mutations in the COL3A1 gene have been implicated as a cause of type IV Ehlers-Danlos syndrome, a disease leading to aortic rupture in early adult life. The mutated allele was transmitted through the mouse germ line and homozygous mutant animals were derived from heterozygous intercrosses. About 10% of the homozygous mutant animals survived to adulthood but have a much shorter life span compared with wild-type mice. The major cause of death of mutant mice was rupture of the major blood vessels, similar to patients with type IV Ehlers-Danlos syndrome. Type III collagen is essential for normal collagen I fibrillogenesis in the cardiovascular system and other organs.
Type-IV collagen is a type of collagen found primarily in the basal lamina. The C-terminus domain is not removed in post-translational processing, and the fibers link head-to-head, rather than in parallel. Also, type-IV lacks the regular glycine in every third residue necessary for the tight, collagen helix. This makes the overall arrangement more sloppy with kinks. These two features cause the collagen to form in a sheet, the form of the basal lamina.
All of the type IV collagen in mammals is derived from six genetically distinct a-chain polypeptides (a1–a6). The type IV collagen a-chains have similar domain structures and share between 50–70% homology at the amino-acid level. The a-chains can be separated into three domains: an amino-terminal 7S domain, a middle triple-helical domain, and a carboxy-terminal globular non-collagenous (NC)-1 domain (see figure).
Type-V collagen is a form of fibrillar collagen associated with classical Ehlers-Danlos syndrome.Type V collagen is found in tissues containing type I collagen and appears to regulate the assembly of heterotypic fibers composed of both type I and type V collagen. This gene product is closely related to type XI collagen and it is possible that the collagen chains of types V and XI constitute a single collagen type with tissue-specific chain combinations. Collagen type V is highly expressed during tissue development and wound repair, but its exact function remains unclear. Cell binding to collagen V affects various basic cell functions and increased collagen V levels alter the structural organization and the stiffness of the ECM. Collagen V plays an essential role in modifying cell behavior during development and remodeling, when very soft tissues are present.
gen VI is a form of collagen primarily associated with the extracellular matrix of skeletal muscle.It is associated with the genes COL6A1, COL6A2, and COL6A3.Defects are associated with Bethlem myopathy and Ullrich congenital muscular dystrophy.
Collagen VI is a major structural component of microfibrils. The basic structural unit of collagen VI is a heterotrimer of the alpha1(VI), alpha2(VI), and alpha3(VI) chains. The alpha2(VI) and alpha3(VI) chains are encoded by the COL6A2 and COL6A3 genes, respectively. The protein encoded by this gene is the alpha 1 subunit of type VI collagen (alpha1(VI) chain). Mutations in the genes that code for the collagen VI subunits result in the autosomal dominant disorder, Bethlem myopathy.
Collagen, type VII, alpha 1 encodes the alpha chain of type VII collagen. The type VII collagen fibril, composed of three identical alpha collagen chains, is restricted to the basement zone beneath stratified squamous epithelia. It functions as an anchoring fibril between the external epithelia and the underlying stroma.
Mutations in this gene are associated with all forms of dystrophic epidermolysis bullosa. In the absence of mutations, however, an autoimmune response against type VII collagen can result in an acquired form of this disease called epidermolysis bullosa acquisita.Type VII collagen is also found in the retina; its function in this organ is unknown.COL7A1 is located on the short arm of human chromosome 3, in the chromosomal region denoted 3p21.31.
