cartilage associated protein
The CRTAP gene provides instructions for making a protein called cartilage associated protein. While the specific function of this protein is not known, it plays an important role in normal bone development. Cartilage associated protein works with two other proteins, leprecan and cyclophilin B, as part of a complex that helps process certain forms of collagen. Collagens are proteins that provide strength, support, and the ability to stretch (elasticity) to many body tissues.
The complex containing cartilage associated protein modifies a protein building block (amino acid) called proline in collagen molecules. This modification, which is known as proline 3-hydroxylation, appears to be critical for the normal folding and assembly of collagen. It also may be important for releasing collagen molecules into the spaces around cells (the extracellular matrix). The secretion of collagen from cells is necessary for the proper formation of connective tissues, such as bones, tendons, and cartilage, that form the body's supportive framework.
At least five mutations in the CRTAP gene are responsible for a rare type of osteogenesis imperfecta that is usually classified as type VII. Several of these mutations prevent cells from producing any cartilage associated protein. Without this protein, bones and other connective tissues do not form properly, leading to a very severe form of the disorder. Another mutation in the CRTAP gene greatly reduces the amount of cartilage associated protein produced, which disrupts the normal formation of collagen. This genetic change causes less severe signs and symptoms of osteogenesis imperfecta.
- cartilage-associated protein
- Howard Hughes Medical Institute: Genetic Mutation Explains Form of Brittle Bone Disease (October 20, 2006)
- Molecular Biology of the Cell (fourth edition, 2002): Collagens Are the Major Proteins of the Extracellular Matrix
- Molecular Cell Biology (fourth edition, 2000): Collagen: The Fibrous Proteins of the Matrix
- The Cell: A Molecular Approach (second edition, 2000): Collagen fibrils (figure)