Sandbox Reserved 381: Difference between revisions

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O-linked beta-N-acetylglucosamine transferase (O-GlcNAc transferase) is an essential mammalian enzyme that acts as a nutrient sensor, coupling metabolic status to the regulation of a wide variety of cellular signaling pathways.<ref> Hart GW, Housley MP, Slawson C. Cycling of O-linked beta-N-acetylglucosamine on nucleocytoplasmic proteins. Nature.2007;446:1017-22.[http://www.nature.com/nature/journal/v446/n7139/abs/nature05815.html]</ref> OGT catalyses the transfer of N-acetylglucosamine from UDP-N-acetylglucosamine (UDP-GlcNAc) to serines and threonines of cytoplasmic, nuclear and mitochondrial proteins, including numerous transcription factors, tumour suppressors, kinases, phospahateses and histone-modifying proteins.<ref>PMID:21240259</ref> Two crystal structures of human OGT are reported here, as a binary complex with UDP (2.8 A resolution) and as a ternary complex with UDP and a peptide substrate (1.95 A).
O-linked beta-N-acetylglucosamine transferase (O-GlcNAc transferase) is an essential mammalian enzyme that acts as a nutrient sensor, coupling metabolic status to the regulation of a wide variety of cellular signaling pathways.<ref> Hart GW, Housley MP, Slawson C. Cycling of O-linked beta-N-acetylglucosamine on nucleocytoplasmic proteins. Nature.2007;446:1017-22.[http://www.nature.com/nature/journal/v446/n7139/abs/nature05815.html]</ref> OGT catalyses the transfer of N-acetylglucosamine from UDP-N-acetylglucosamine (UDP-GlcNAc) to serines and threonines of cytoplasmic, nuclear and mitochondrial proteins, including numerous transcription factors, tumour suppressors, kinases, phospahateses and histone-modifying proteins.<ref>PMID:21240259</ref> Two crystal structures of human OGT are reported here, as a binary complex with UDP (2.8 A resolution) and as a ternary complex with UDP and a peptide substrate (1.95 A).


[[Image:Scheme of O-GlcNAcylation.jpg|thumb|200px|left|Scheme of O-GlcNAcylation.<ref> The O-linked N-acetylglucosamine modification in cellular signalling and the immune system  [image on the internet]. 2008[cited 2011 Nov 22]. Available from: http://www.nature.com/embor/journal/v9/n8/full/embor2008129.html</ref>]]


== O-GlcNAc Modifications ==
== O-GlcNAc Modifications ==


O-GlcNAc modification has been described for a large and still increasing number of proteins, many of which are key modulators of cellular signalling.  O-GlcNAc modifications are catalysed by a glycosyltransferase named O-linked N-acetylglucosaminyltranserase (OGT), and are removed by the antagonistic enzyme B-N-acetylglucosaminidase (O-GlcNAcase). The general scheme of O-linked N-acetylglucosamine modification depicted here suggests that N-acetylglucosamine is added to serine/threonine (Ser/Thr) residues of target proteins by the enzyme OGT using UDP-GlcNac as substrate.  The N-acetylglucosamine group is removed by the antagonistic activity of O-GlcNAcase. <ref>PMID:11807088</ref>
O-GlcNAc modification has been described for a large and still increasing number of proteins, many of which are key modulators of cellular signalling.  O-GlcNAc modifications are catalysed by a glycosyltransferase named O-linked N-acetylglucosaminyltranserase (OGT), and are removed by the antagonistic enzyme B-N-acetylglucosaminidase (O-GlcNAcase). The general scheme of O-linked N-acetylglucosamine modification suggests that N-acetylglucosamine is added to serine/threonine (Ser/Thr) residues of target proteins by the enzyme OGT using UDP-GlcNac as substrate.  The N-acetylglucosamine group is removed by the antagonistic activity of O-GlcNAcase. <ref>PMID:11807088</ref>


== Gangliosides ==
== Gangliosides ==
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