Abstract
In eukaryotes, glycosylation plays a role in proteome stability, protein quality control, and modulating protein function; however, similar studies in bacteria are lacking. Here, we investigate the roles of general protein glycosylation systems in bacteria using the enteropathogen Campylobacter jejuni as a well-defined example. By using a quantitative proteomic strategy, we were able to monitor changes in the C. jejuni proteome when glycosylation is disrupted. We demonstrate that in C. jejuni, N-glycosylation is essential to maintain proteome stability and protein quality control. These findings guided us to investigate the role of N-glycosylation in modulating bacterial cellular activities. In glycosylation-deficient C. jejuni, the multidrug efflux pump and electron transport pathways were significantly impaired. We demonstrate that in vivo, fully glycosylation-deficient C. jejuni bacteria were unable to colonize its natural avian host. These results provide the first evidence of a link between proteome stability and complex functions via a bacterial general glycosylation system.IMPORTANCE Advances in genomics and mass spectrometry have revealed several types of glycosylation systems in bacteria. However, why bacterial proteins are modified remains poorly defined. Here, we investigated the role of general N-linked glycosylation in a major food poisoning bacterium, Campylobacter jejuni The aim of this study is to delineate the direct and indirect effects caused by disrupting this posttranslational modification. To achieve this, we employed a quantitative proteomic strategy to monitor alterations in the C. jejuni proteome. Our quantitative proteomic results linked general protein N-glycosylation to maintaining proteome stability. Functional analyses revealed novel roles for bacterial N-glycosylation in modulating multidrug efflux pump, enhancing nitrate reduction activity, and promoting host-microbe interaction. This work provides insights on the importance of general glycosylation in proteins in maintaining bacterial physiology, thus expanding our knowledge of the emergence of posttranslational modification in bacteria.
Highlights
In eukaryotes, glycosylation plays a role in proteome stability, protein quality control, and modulating protein function; similar studies in bacteria are lacking
We detected GroL, a periplasmic chaperone that binds to unfolded and partially folded proteins promoting folding [13], HtpG, a chaperone involved in binding to aggregated proteins and protecting the cell against environmental stresses [14], and Cj0694, a peptidyl-prolyl-cis/trans isomerase (PPIase) that interacts with the Sec translocon and promotes folding of polypeptides emerging from
Our results provide in-depth analyses on the alteration of the C. jejuni proteome as a consequence of disrupting the N-linked protein glycosylation pathway
Summary
Glycosylation plays a role in proteome stability, protein quality control, and modulating protein function; similar studies in bacteria are lacking. We demonstrate that in C. jejuni, N-glycosylation is essential to maintain proteome stability and protein quality control These findings guided us to investigate the role of N-glycosylation in modulating bacterial cellular activities. We demonstrate that in vivo, fully glycosylation-deficient C. jejuni bacteria were unable to colonize its natural avian host These results provide the first evidence of a link between proteome stability and complex functions via a bacterial general glycosylation system. Contrary to current understanding, the loss of glycosylation predominantly has a mass effect on the C. jejuni proteome, rather than being restricted exclusively to proteins modified by glycosylation This resulted in reduction in multidrug efflux pump activity as well as impairment in nitrate reductase activity. This study provides deeper insights on the role of a general N-glycosylation system in bacteria, demonstrating that protein posttranslational modification is critical to a plethora of bacterial cellular activities
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