Post-translational Modification of Extremophilic Proteins: N-glycosylation in Archaea.

摘要

Found in the harshest environments on Earth, Archaea express proteins that remain functional in the face of conditions that would otherwise lead to denaturation and aggregation. Post-translational modifications, like glycosylation, help protect archaeal proteins from such fates. Better understanding of archaeal protein glycosylation would thus provide insight into how extremophilic proteins overcome the challenges of their environments. In previous ARL-funded work, we defined a series of Agl proteins involved in the assembly and attachment of a novel pentasaccharide to select asparagine residues of the surface-layer glycoprotein of the model archaeon, Haloferax volcanii. In the recently ended project, we 1) identified and characterized novel Agl proteins, 2) revealed the ability of the Hfx. volcanii N-glycosylation pathway to modify non-native target proteins, 3) described components involved in the biogenesis of the dolichol phosphate that serves as glycan carrier during Hfx. volcanii N-glycosylation, 4) delineated a novel Hfx. volcanii N-glycosylation pathway recruited by cells grown at low salinity, 5) assessed the distribution of N-glycosylation pathway components across the Archaea, 6) identified two populations of the reporter Hfx. volcanii glycoprotein, the S-layer glycoprotein, one modified by a lipid anchor, the other presenting a transmembrane domain, 7) revealed the promiscuity of the archaeal oligosaccharyltransferase, AglB, 8) created the aglgenes database for cataloguing available information on the enzymes of archaeal N-glycosylation and 9) began deciphering the N-glycosylation pathways of Archaea other than Hfx. volcanii.