The S-Layer Glycoprotein of the Crenarchaeote Sulfolobus acidocaldarius Is Glycosylated at Multiple Sites with Chitobiose-Linked N-Glycans

Abstract EN

Glycosylation of the S-layer of the crenarchaea Sulfolobus acidocaldarius has been investigated using glycoproteomic methodologies.

The mature protein is predicted to contain 31 N-glycosylation consensus sites with approximately one third being found in the C-terminal domain spanning residues L1004-Q1395.

Since this domain is rich in Lys and Arg and therefore relatively tractable to glycoproteomic analysis, this study has focused on mapping its N-glycosylation.

Our analysis identified nine of the 11 consensus sequence sites, and all were found to be glycosylated.

This constitutes a remarkably high glycosylation density in the C-terminal domain averaging one site for each stretch of 30–40 residues.

Each of the glycosylation sites observed was shown to be modified with a heterogeneous family of glycans, with the largest having a composition Glc1Man2GlcNAc2 plus 6-sulfoquinovose (QuiS), consistent with the tribranched hexasaccharide previously reported in the cytochrome b558/566 of S.

acidocaldarius.

S.

acidocaldarius is the only archaeal species whose N-glycans are known to be linked via the chitobiose core disaccharide that characterises the N-linked glycans of Eukarya.