Post-translational modifications?
The biosynthesis of collagen has several post-translational modificiations on the pro-alpha chains. Hydroxylation of proline and lysine and Glycoslyation of hydroxylysine. I fully understand the hydroxylation of the amino acids, but I am sturggling to understand the glycoslyation of the hydroxylysine. Does anyone know how to explain it properly?
Answers:
Glycosylation is the addition of a sugar to one of the residues of the target protein. Additions that are on the –OH of serine or threonine are called O-linked glycosylation. The addition of the hydroxyl group to lysine in collagen permits a similar addition to occur where a glycosidic bond is formed to the hydroxylysine sidechain.
If you wanted to know about the chemical reaction mechanism, then I suggest looking at a standard college biochemistry textbook. An online text is available for free at:
http://www.ncbi.nlm.nih.gov/entrez/query.
This is a more specialized reference but it probably will tell you much more than you ever wanted to know about post-translational modification of collagens.
http://www.springerlink.com/content/hrc3.
Wibble........
If you're asking why it's glycosyated, I can tell you that many proteins that reside in extracellular spaces (like collagen usually does) have carbohydrates attached to them at some point. These are referred to as 'glycoproteins'. The glycosylation of hydroxylysine is the unique way that the enzymes that make collagen (ie; that modify the collagen protein post translation, in the ER) bind a sugar molecule onto the protein (I think its usually galactose, but I'm not sure).
The sugar molecules help collagen assume its mature structure, and interact with other collagen molecules. If you're asking about how the enzymes add the sugars, I have no idea.
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Answers:
Glycosylation is the addition of a sugar to one of the residues of the target protein. Additions that are on the –OH of serine or threonine are called O-linked glycosylation. The addition of the hydroxyl group to lysine in collagen permits a similar addition to occur where a glycosidic bond is formed to the hydroxylysine sidechain.
If you wanted to know about the chemical reaction mechanism, then I suggest looking at a standard college biochemistry textbook. An online text is available for free at:
http://www.ncbi.nlm.nih.gov/entrez/query.
This is a more specialized reference but it probably will tell you much more than you ever wanted to know about post-translational modification of collagens.
http://www.springerlink.com/content/hrc3.
Wibble........
If you're asking why it's glycosyated, I can tell you that many proteins that reside in extracellular spaces (like collagen usually does) have carbohydrates attached to them at some point. These are referred to as 'glycoproteins'. The glycosylation of hydroxylysine is the unique way that the enzymes that make collagen (ie; that modify the collagen protein post translation, in the ER) bind a sugar molecule onto the protein (I think its usually galactose, but I'm not sure).
The sugar molecules help collagen assume its mature structure, and interact with other collagen molecules. If you're asking about how the enzymes add the sugars, I have no idea.
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