AglQ is a novel component of the Haloferax volcanii N-glycosylation pathway.
N-glycosylation is a post-translational modification performed by members of all three domains of life. Studies on the halophile Haloferax volcanii have offered insight into the archaeal version of this universal protein-processing event. In the present study, AglQ was identified as a novel component of the pathway responsible for the assembly and addition of a pentasaccharide to select Asn residues of Hfx. volcanii glycoproteins, such as the S-layer glycoprotein. In cells deleted of aglQ, both dolichol phosphate, the lipid carrier used in Hfx. volcanii N-glycosylation, and modified S-layer glycoprotein Asn residues only presented the first three pentasaccharide subunits, pointing to a role for AglQ in either preparing the third sugar for attachment of the fourth pentasaccharide subunit or processing the fourth sugar prior to its addition to the lipid-linked trisaccharide. To better define the precise role of AglQ, shown to be a soluble protein, bioinformatics tools were recruited to identify sequence or structural homologs of known function. Site-directed mutagenesis experiments guided by these predictions identified residues important for AglQ function. The results obtained point to AglQ acting as an isomerase in Hfx. volcanii N-glycosylation.
Department of Life Sciences, Ben Gurion University, Beersheva, Israel.
Adi
A
Arbiv
Sophie
S
Yurist-Doutsch
Ziqiang
Z
Guan
Jerry
J
Eichler
D000596:Amino Acids / Q000737:chemistry; D019843:Archaeal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D019295:Computational Biology / Q000379:methods; D017353:Gene Deletion; D015870:Gene Expression; D006023:Glycoproteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006031:Glycosylation; D019622:Haloferax volcanii / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D012995:Solubility
D000596:Amino Acids; D019843:Archaeal Proteins; D006023:Glycoproteins