Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
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In this study, characterization of the N-glycosylation process in the haloarchaea Haloferax volcanii was undertaken. Initially, putative Hfx. volcanii homologues of genes involved in eukaryal or bacterial N-glycosylation were identified by bioinformatics. Reverse transcription polymerase chain reaction (RT-PCR) confirmed that the proposed N-glycosylation genes are transcribed, indicative of true proteins being encoded. Where families of related gene sequences were detected, differential transcription of family members under a variety of physiological and environmental conditions was shown. Gene deletions point to certain genes, like alg11, as being essential yet revealed that others, such as the two versions of alg5, are not. Deletion of alg5-A did, however, lead to slower growth and interfered with surface (S)-layer glycoprotein glycosylation, as detected by modified migration on SDS-PAGE and glycostaining approaches. As deletion of stt3, the only component of the oligosaccharide transferase complex detected in Archaea, did not affect cell viability, it appears that N-glycosylation is not essential in Hfx. volcanii. Deletion of stt3 did, nonetheless, hinder both cell growth and S-layer glycoprotein glycosylation. Thus, with genes putatively involved in Hfx. volcanii protein glycosylation identified and the ability to address the roles played by the encoded polypeptides in modifying a reporter glycoprotein, the steps of the archaeal N-glycosylation pathway can be defined.
Mol Microbiol 2006 Jul
PMID:Protein N-glycosylation in Archaea: defining Haloferax volcanii genes involved in S-layer glycoprotein glycosylation. 1676 24

Post-translational modifications account for much of the biological diversity generated at the proteome level. Of these, glycosylation is the most prevalent. Long thought to be unique to Eukarya, it is now clear that both Bacteria and Archaea are also capable of N-glycosylation, namely the covalent linkage of oligosaccharides to select target asparagine residues. However, while the eukaryal and bacterial N-glycosylation pathways are relatively well defined, little is known of the parallel process in Archaea. Of late, however, major advances have been made in describing the process of archaeal N-glycosylation. Such efforts have shown, as is often the case in archaeal biology, that protein N-glycosylation in Archaea combines particular aspects of the eukaryal and bacterial pathways along with traits unique to this life form. For instance, while the oligosaccharides of archaeal glycoproteins include nucleotide-activated sugars formed by bacterial pathways, the lipid carrier on which such oligosaccharides are assembled is the same as used in eukaryal N-glycosylation. By contrast, transfer of assembled oligosaccharides to their protein targets shows Archaea-specific properties. Finally, addressing N-glycosylation from an archaeal perspective is providing new general insight into this event, as exemplified by the solution of the first crystal structure of an oligosaccharide transferase from an archaeal source.
Mol Microbiol 2008 Jun
PMID:Sweet to the extreme: protein glycosylation in Archaea. 1847 20

Proteins in all three domains of life can experience N-glycosylation. The steps involved in the archaeal version of this post-translational modification remain largely unknown. Hence, as the next step in ongoing efforts to identify components of the N-glycosylation pathway of the halophilic archaeon Haloferax volcanii, the involvement of three additional gene products in the biosynthesis of the pentasaccharide decorating the S-layer glycoprotein was demonstrated. The genes encoding AglF, AglI and AglG are found immediately upstream of the gene encoding the archaeal oligosaccharide transferase, AglB. Evidence showing that AglF and AglI are involved in the addition of the hexuronic acid found at position three of the pentasaccharide is provided, while AglG is shown to contribute to the addition of the hexuronic acid found at position two. Given their proximities in the H. volcanii genome, the transcription profiles of aglF, aglI, aglG and aglB were considered. While only aglF and aglI share a common promoter, transcription of the four genes is co-ordinated, as revealed by determining transcript levels in H. volcanii cells raised in different growth conditions. Such changes in N-glycosylation gene transcription levels offer additional support for the adaptive role of this post-translational modification in H. volcanii.
Mol Microbiol 2008 Sep
PMID:AglF, aglG and aglI, novel members of a gene island involved in the N-glycosylation of the Haloferax volcanii S-layer glycoprotein. 1863 Dec 42

The trafficking of the mu-opioid receptor (MOR), a member of the rhodopsin G protein-coupled receptor (GPCR) family, can be regulated by interaction with multiple cellular proteins. To determine the proteins involved in receptor trafficking, using the targeted proteomic approach and mass spectrometry analysis, we have identified that Ribophorin I (RPNI), a component of the oligosaccharide transferase complex, could directly interact with MOR. RPNI can be shown to participate in MOR export by the intracellular retention of the receptor after small interfering RNA knockdown of endogenous RPNI. Overexpression of RPNI rescued the surface expression of the MOR 344KFCTR348 deletion mutant independent of calnexin. Furthermore, RPNI regulation of MOR trafficking is dependent on the glycosylation state of the receptor, as reflected by the inability of overexpression of RPNI to affect the trafficking of the N-glycosylation-deficient mutants, or GPCRs that have minimal glycosylation sites. Hence, this novel RPNI chaperone activity is a consequence of N-glycosylation-dependent direct interaction with MOR.
Mol Pharmacol 2009 Jun
PMID:mu-Opioid receptor cell surface expression is regulated by its direct interaction with Ribophorin I. 1928 71