General N-and O-Linked Glycosylation of Lipoproteins in Mycoplasmas and Role of Exogenous Oligosaccharide

Abstract

The lack of a cell wall, flagella, fimbria, and other extracellular appendages and the possession of only a single membrane render the mycoplasmas structurally simplistic and ideal model organisms for the study of glycoconjugates. Most species have genomes of about 800 kb and code for few proteins predicted to have a role in glycobiology. The murine pathogens Mycoplasma arthritidis and Mycoplasma pulmonis have only a single gene annotated as coding for a glycosyltransferase but synthesize glycolipid, polysaccharide and glycoproteins. Previously, it was shown that M. arthritidis glycosylated surface lipoproteins through O-linkage. In the current study, O-linked glycoproteins were similarly found in M. pulmonis and both species of mycoplasma were found to also possess N-linked glycans at residues of asparagine and glutamine. Protein glycosylation occurred at numerous sites on surface-exposed lipoproteins with no apparent amino acid sequence specificity. The lipoproteins of Mycoplasma pneumoniae also are glycosylated. Glycosylation was dependent on the glycosidic linkages from host oligosaccharides. As far as we are aware, N-linked glycoproteins have not been previously described in Gram-positive bacteria, the organisms to which the mycoplasmas are phylogenetically related. The findings indicate that the mycoplasma cell surface is heavily glycosylated with implications for the modulation of mycoplasma-host interactions.

Ample glycosylation in membrane and cell envelope proteins may explain the phenotypic diversity and virulence in the Mycobacterium tuberculosis complex

“…Protein glycosylation occurred at numerous sites on surface-exposed proteins with no apparent amino acid sequence specificity (Fig. 3) 7 . As previously reported, there is a relatively high propensity for R, A, P, L, G, V, S and T flanking the modified sites in a significant portion of the glycosylation sites mapped 11,27,30 (Fig.…”

“…The unique Mtb glycoconjugates in the cell envelope are the predominant basis for host–pathogen interactions, antigenicity, and virulence determination and constitute one of the major components causing antimicrobial resistance (AMR) in Mtb 1–6 . Glycosylation in Mtb has mainly been detected in surface-exposed proteins and in some other membrane proteins 7 . The unique structure, antigenicity and essentiality of Mtb cell envelope glycoconjugates for mycobacterial growth provide opportunities for the development of novel drugs, vaccines, diagnostics and biomarkers 1 .…”

Mycoplasma pneumoniae lipids license TLR-4 for activation of NLRP3 inflammasome and autophagy to evoke a proinflammatory response

“…This pathogen causes upper and lower respiratory illnesses in all age groups and accounts for 4-8% of communityacquired bacterial pneumonia cases in adults, presenting incidence rates ranging from 20 to 70% during epidemics of sporadic M. pneumoniae in China [2]. M. pneumoniae produces various virulent factors, such as membrane lipoproteins, polysaccharides and invasive nucleases, which cause a series of pathophysiological changes [3][4][5]. Because M. pneumoniae has no cell wall, its cell membrane is the major structure that interacts with the host [3].…”

How Sweet Are Our Gut Beneficial Bacteria? A Focus on Protein Glycosylation in Lactobacillus

“…In fact, evidence for N -glycosylation in mycoplasma species has emerged. In a recent study, Asn and Gln residues outside of the N -glycosylation consensus sequence were found to carry a single Hex in Mycoplasma pulmonis and Mycoplasma arthritis glycoproteins, which could suggest a similar glycosylation mechanism to the one found in Haemophilus infuenzae [ 17 ]. However, no intracellular glycoproteins could be identified, suggesting that this process may take place extracellularly.…”

“…However, no intracellular glycoproteins could be identified, suggesting that this process may take place extracellularly. In addition, it was shown that the bacteria could use free oligosaccharides from the growth media, without the need to synthesize glycans internally to use for protein glycosylation [ 17 ], in support of this mechanism.…”