Effects of N-glycan precursor length diversity on quality control of protein folding and on protein glycosylation.
In: Seminars in Cell & Developmental Biology, Jg. 41 (2015-05-01), S. 121-128
academicJournal
Zugriff:
Asparagine-linked glycans ( N -glycans) of medically important protists have much to tell us about the evolution of N -glycosylation and of N -glycan-dependent quality control ( N -glycan QC) of protein folding in the endoplasmic reticulum. While host N -glycans are built upon a dolichol-pyrophosphate-linked precursor with 14 sugars (Glc 3 Man 9 GlcNAc 2 ), protist N -glycan precursors vary from Glc 3 Man 9 GlcNAc 2 ( Acanthamoeba ) to Man 9 GlcNAc 2 ( Trypanosoma ) to Glc 3 Man 5 GlcNAc 2 ( Toxoplasma ) to Man 5 GlcNAc 2 ( Entamoeba , Trichomonas , and Eimeria ) to GlcNAc 2 ( Plasmodium and Giardia ) to zero ( Theileria ). As related organisms have differing N -glycan lengths (e.g. Toxoplasma , Eimeria , Plasmodium , and Theileria ), the present N -glycan variation is based upon secondary loss of Alg genes, which encode enzymes that add sugars to the N -glycan precursor. An N -glycan precursor with Man 5 GlcNAc 2 is necessary but not sufficient for N -glycan QC, which is predicted by the presence of the UDP-glucose:glucosyltransferase (UGGT) plus calreticulin and/or calnexin. As many parasites lack glucose in their N -glycan precursor, UGGT product may be identified by inhibition of glucosidase II. The presence of an armless calnexin in Toxoplasma suggests secondary loss of N -glycan QC from coccidia. Positive selection for N -glycan sites occurs in secreted proteins of organisms with N -glycan QC and is based upon an increased likelihood of threonine but not serine in the +2 position versus asparagine. In contrast, there appears to be selection against N -glycan length in Plasmodium and N -glycan site density in Toxoplasma . Finally, there is suggestive evidence for N -glycan-dependent ERAD in Trichomonas , which glycosylates and degrades the exogenous reporter mutant carboxypeptidase Y (CPY*). [ABSTRACT FROM AUTHOR]
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Effects of N-glycan precursor length diversity on quality control of protein folding and on protein glycosylation.
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Autor/in / Beteiligte Person: | Samuelson, John ; Robbins, Phillips W. |
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Zeitschrift: | Seminars in Cell & Developmental Biology, Jg. 41 (2015-05-01), S. 121-128 |
Veröffentlichung: | 2015 |
Medientyp: | academicJournal |
ISSN: | 1084-9521 (print) |
DOI: | 10.1016/j.semcdb.2014.11.008 |
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