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Nature. 2005 Oct 27;437(7063):1252.

Protein glycosylation: chaperone mutation in Tn syndrome.

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  • 1Department of Biochemistry and Molecular Biology, and Oklahoma Center for Medical Glycobiology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, USA.


Tn syndrome is a rare autoimmune disease in which subpopulations of blood cells in all lineages carry an incompletely glycosylated membrane glycoprotein, known as the Tn antigen. This truncated antigen has the sugar N-acetylgalactosamine alpha-linked to either a serine or threonine amino-acid residue, whereas the correct T antigen has an additional terminal galactose; the defect may be due to a malfunction of the glycosylating enzyme T-synthase. Here we show that Tn syndrome is associated with a somatic mutation in Cosmc, a gene on the X chromosome that encodes a molecular 'chaperone' that is required for the proper folding and hence full activity of T-synthase. The production of the autoimmune Tn antigen by a glycosyltransferase enzyme rendered defective by a disabled chaperone may have implications for other Tn-related disorders such as IgA nephropathy, a condition that can result in renal failure.

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