Protein glycosylation as an adaptive response in Archaea: growth at different salt concentrations leads to alterations in Haloferax volcanii S‐layer glycoprotein N‐glycosylation

Abstract

Summary To cope with life in hypersaline environments, halophilic archaeal proteins are enriched in acidic amino acids. This strategy does not, however, offer a response to transient changes in salinity, as would post-translational modifications. To test this hypothesis, N-glycosylation of the Haloferax volcanii S-layer glycoprotein was compared in cells grown in high (3.4 M NaCl) and low (1.75 M NaCl) salt, as was the glycan bound to dolichol phosphate, the lipid upon which the N-linked glycan is assembled. In high salt, S-layer glycoprotein Asn-13 and Asn-83 are modified by a pentasaccharide, while dolichol phosphate is modified by a tetrasaccharide comprising the first four pentasaccharide residues. When the same targets were considered from cells grown in low salt, substantially less pentasaccharide was detected. At the same time, cells grown at low salinity contain dolichol phosphate modified by a distinct tetrasaccharide absent in cells grown at high salinity. The same tetrasaccharide modified S-layer glycoprotein Asn-498 in cells grown in low salt, whereas no glycan decorated this residue in cells grown in the high-salt medium. Thus, in response to changes in environmental salinity, Hfx. volcanii not only modulates the N-linked glycans decorating the S-layer glycoprotein but also the sites of such post-translational modification.

Comparative Analysis of Archaeal Lipid-linked Oligosaccharides That Serve as Oligosaccharide Donors for Asn Glycosylation

“…The complexity of the archaeal N-glycoproteome is probably for the adaptation against harsh environments. The transfer of a tetrasaccharide chain onto the H. volcanii S-layer protein in response to low salt culture conditions provides a good precedent for the adaptation to environmental changes (42). A similar adaptive mechanism was discussed for the lower Eukaryote, Protozoa.…”

A Rhomboid Protease Gene Deletion Affects a Novel Oligosaccharide N-Linked to the S-layer Glycoprotein of Haloferax volcanii

“…The S-layer glycoprotein from H. volcanii has been reported to bear a pentasaccharide of known composition at positions Asn-13 and Asn-83 as well as a sulfated tetrasaccharide at position Asn-379, which is present in low salt conditions (19). However, there have been no reports on N-acetylglucosamine N-linked long chain oligosaccharides for this protein.…”

“…However, the possible modification of Asn-274, Asn-279, and Asn-732 has not been reported so far (19). Therefore, it was important to determine the binding site(s) of this novel oligosaccharide.…”

“…However, when cells were grown in low salt, substantially less pentasaccharide was detected, whereas a distinct tetrasaccharide composed by three hexoses (one of them sulfated) and a rhamnose, which is absent in cells grown at high salinity, was found at Asn-498. Thus, in response to changes in environmental salinity, H. volcanii modulates not only the N-linked glycans decorating the S-layer glycoprotein but also the sites of such posttranslational modification (19). Recently, it has been reported that two different glycosylation pathways participate in the synthesis of the tetra-and pentasaccharide (20).…”

Mannoside recognition and degradation by bacteria

“…However, the presence of a glycan coating is strongly associated with survival in harsh environments. For instance, variability in N-glycan pattern occurs in the halophilic archaeon Haloferax volcanii WR536 (H53), depending on the salt concentration (Guan et al, 2012), while the extreme halophile Halobacterium halobium DS2 produces sulfated or uronic acids containing N-glycans in the presence of high salt concentrations (Mengele & Sumper, 1992). Finally, in archaea, N-glycans are attached to proteins in the same N-x-S/T (x =P) sequon as in eukaryotes, although an additional N-x-N/L/V sequon has also been reported in Halobacterium halobium DSM670 (Zeitler et al, 1998).…”