Collagen Structure & Function: Difference between revisions
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==Introduction== | ==Introduction== | ||
Collagen is a member of a family of naturally occurring proteins. It is one of the most plentiful proteins present in mammals and it is responsible for performing a variety of important biological functions. It is most well-known for the structural role it plays in the body. It is present in large quantities in connective tissue and provides tendons and ligaments with tensile strength and skin with elasticity. It often works in conjuction with other important proteins such as keratin and elastin. | Collagen is a member of a family of naturally occurring proteins. It is one of the most plentiful proteins present in mammals and it is responsible for performing a variety of important biological functions. It is most well-known for the structural role it plays in the body. It is present in large quantities in connective tissue and provides tendons and ligaments with tensile strength and skin with elasticity. It often works in conjuction with other important proteins such as keratin and elastin. | ||
==Biosynthesis== | |||
Collagen synthesis begins in fibroblasts <ref name="biosyn">PMID:PMC1367617</ref>.It is here that amino acids undergo activation; Proline is hydroxylated to Hydroxyproline and Lysine to Hydroxylysine. Peptide subunits of ~250 residues are assembled on the ribosome and are linked by carbohydrate residues to form α-chains <ref name="biosyn" />. Three α-chains then associate with each other and then associate extracelluarly. During the process of collagen synthesis, free-hydroxyproline and hydroxylysine peptides appear as by-products, some of which are metabolized and may appear in urine <ref name="biosyn" />. | |||
==Molecular Structure== | ==Molecular Structure== | ||
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The triple-helical domain structure of collagens consists of three distinct α-chains and earns collagen the name "tropocollagen".<ref name="collalike">PMID:7695699</ref>. Each of these chains contain a characteristic L-handed amino acid sequence of polyproline, often termed as polyproline type II helix <ref>PMID: 19344236</ref>. The proper folding of each of these chains requires a glycine residue to be present in every third position in the polypeptide chain. For example, each α-chain is composed of multiple triplet sequences of of Gly-Y-Z in which Y and Z can be any amino acid. Y is commonly found as proline and Z is usually present as hydroxyproline (Figure 1.). The presence of hydroxyproline in the Y position is also thought to contribute to the stability of the helical form | The triple-helical domain structure of collagens consists of three distinct α-chains and earns collagen the name "tropocollagen".<ref name="collalike">PMID:7695699</ref>. Each of these chains contain a characteristic L-handed amino acid sequence of polyproline, often termed as polyproline type II helix <ref>PMID: 19344236</ref>. The proper folding of each of these chains requires a glycine residue to be present in every third position in the polypeptide chain. For example, each α-chain is composed of multiple triplet sequences of of Gly-Y-Z in which Y and Z can be any amino acid. Y is commonly found as proline and Z is usually present as hydroxyproline (Figure 1.). The presence of hydroxyproline in the Y position is also thought to contribute to the stability of the helical form <ref name="collalike" />. | ||