Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0038362 (stomatitis)
 8,852 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The biochemical and kinetic properties of UDP-GlcNAc:alpha-D-mannoside (GlcNAc to Man alpha 1,3) beta 1,2-N-acetylglucosaminyltransferase I (GlcNAc-TI) have been investigated in the Chinese hamster ovary glycosylation mutant Lec1A. Previous studies showed that, whereas Lec1A cells synthesize complex carbohydrates at levels consistent with partial GlcNAc-TI action, no GlcNAc-TI activity was detected in Lec1A cell-free extracts (Stanley, P., and Chaney, W. (1985) Mol. Cell. Biol. 5, 1204-1211). It is now reported that, under altered reaction conditions, GlcNAc-TI activity can be measured in Lec1A cell extracts. The GlcNAc-TI enzyme in Lec1A.2C has a pH optimum of 7.5 (compared with 6.25 for the parental enzyme) and apparent Km values for Man5GlcNAc2Asn and UDP-GlcNAc that are, respectively, 21- and 44-fold higher than the apparent Km values of GlcNAc-TI from parental Chinese hamster ovary cells. Two independent Lec1A mutants possess GlcNAc-TI activities with similarly altered biochemical and kinetic properties. In fact, under optimal assay conditions for each cell line, the level of GlcNAc-TI in Lec1A extracts is equal to that of parental Chinese hamster ovary cell extracts. Interestingly, the two glycosylation sites of the G glycoprotein of vesicular stomatitis virus are processed quite differently in Lec1A cells. The glycopeptide nearest the carboxyl-terminal appears to be a preferred substrate for the Lec1A GlcNAc-TI activity. The combined data suggest that the Lec1A mutation affects the gene that codes for GlcNAc-TI, giving rise to a structurally altered glycosyltransferase with different biochemical properties.
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PMID:Lec1A Chinese hamster ovary cell mutants appear to arise from a structural alteration in N-acetylglucosaminyltransferase I. 294 43

Lec1 CHO cell glycosylation mutants are defective in N-acetylglucosaminyltransferase I (GlcNAc-TI) activity and therefore cannot convert the oligomannosyl intermediate (Man5GlcNAc2Asn) into complex carbohydrates. Lec1A CHO cell mutants have been shown to belong to the same genetic complementation group but exhibit different phenotypic properties. Evidence is presented that lec1A represents a new mutation at the lec1 locus resulting in partial loss of GlcNAc-TI activity. Structural studies of the carbohydrates associated with vesicular stomatitis virus grown in Lec1A cells (Lec1A/VSV) revealed the presence of biantennary and branched complex carbohydrates as well as the processing intermediate Man5GlcNAc2Asn. By contrast, the glycopeptides from virus grown in CHO cells (CHO/VSV) possessed only fully processed complex carbohydrates, whereas those from Lec1/VSV were almost solely of the Man5GlcNAc2Asn intermediate type. Therefore, the Lec1A glycosylation phenotype appears to result from the partial processing of N-linked carbohydrates because of reduced GlcNAc-TI action on membrane glycoproteins. Genetic experiments provided evidence that lec1A is a single mutation affecting GlcNAc-TI activity. Lec1A mutants could be isolated at frequencies of 10(-5) to 10(-6) from unmutagenized CHO cell populations by single-step selection, a rate inconsistent with two mutations. In addition, segregants selected from Lec1A X parental cell hybrid populations expressed only Lec1A or related lectin-resistant phenotypes and did not include any with a Lec1 phenotype. The Lec1A mutant should be of interest for studies on the mechanisms that control carbohydrate processing in animal cells and the effects of reduced GlcNAc-TI activity on the glycosylation, translocation, and compartmentalization of cellular glycoproteins.
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PMID:Control of carbohydrate processing: the lec1A CHO mutation results in partial loss of N-acetylglucosaminyltransferase I activity. 299 57

We have examined and compared the host-cell-dependent glycosylation of the G glycoprotein of vesicular-stomatitis virus (Hazelhurst strain) and the E1 and E2 glycoproteins of Sindbis virus replicated by baby-hamster kidney, chicken-embryo fibroblast and mouse L929 monolayer cell cultures. The results of endo-beta-N-acetylglucosaminidase H digestion of viral proteins labelled with [3H]mannose or leucine and Pronase-digested glycopeptides labelled with [3H]mannose indicated that both the G protein and the E1 protein contained a similar mixture of endoglycosidase-resistant oligosaccharides of the complex acidic type and less extensively processed endoglycosidase-sensitive oligosaccharides of the neutral or hybrid type, with a relatively greater content of the endoglycosidase-sensitive oligosaccharides for virus replicated in the chicken as against hamster or mouse cells. A large fraction of the G protein and the majority of the E1 proteins from the mammalian host cells contained acidic-type oligosaccharides at both glycosylation sites, whereas most of the G and E1 glycoproteins from the avian host cells and essentially all of the E2 protein from all three host-cell types contained an acidic-type oligosaccharide at one site and neutral- or hybrid-type oligosaccharide at the other site. The relative increase in neutral- and hybrid-type oligosaccharides with five-mannose core structures observed for the G and E1 proteins of virus released from the avian host cells suggested that two specific steps in oligosaccharide processing (mediated by alpha-mannoside II and N-acetylglucosaminyltransferase I) were less efficient at one of the glycosylation sites of the vesicular-stomatitis-virus G protein and Sindbis-virus E1 protein in the avian as against mammalian host cells.
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PMID:Hazelhurst-vesicular-stomatitis-virus G and Sindbis-virus E1 glycoproteins undergo similar host-cell-dependent variation in oligosaccharide processing. 299 31