Erratum: Corrigendum: Arginine-rhamnosylation as new strategy to activate translation elongation factor P

N-glycosylation of a cargo protein C-terminal domain recognized by the type IX secretion system in Cytophaga hutchinsonii affects protein secretion and localization

Cytophaga hutchinsonii is a Gram-negative bacterium belonging to the phylum Bacteroidetes. It digests crystalline cellulose with an unknown mechanism, and possesses a type IX secretion system (T9SS) that can recognize the C-terminal domain (CTD) of the cargo protein as a signal. In this study, the functions of CTD in the secretion and localization of T9SS substrates in C. hutchinsonii were studied by fusing the green fluorescent protein (GFP) with CTD from CHU_2708. CTD is necessary for the secretion of GFP by C. hutchinsonii T9SS. The GFP-CTD_{CHU_2708} fusion protein was found to be glycosylated in the periplasm with a molecular mass about 5 kDa higher than that predicted from its sequence. The glycosylated protein was sensitive to peptide-N-glycosidase F which can hydrolyze N-linked oligosaccharides. Analyses of mutants obtained by site-directed mutagenesis of asparagine residues in the N-X-S/T motif of CTD_{CHU_2708} suggest that N-glycosylation occurred on the CTD. CTD N-glycosylation is important for the secretion and localization of GFP-CTD recombinant proteins in C. hutchinsonii. Glycosyltransferase encoding gene chu_3842, a homologous gene of Campylobacter jejuni pglA, was found to participate in the N-glycosylation of C. hutchinsonii. Deletion of chu_3842 affected cell motility, cellulose degradation, and cell resistance to some chemicals. Our study provided the evidence that CTD as the signal of T9SS was N-glycosylated in the periplasm of C. hutchinsonii. IMPORTANCE The bacterial N-glycosylation system has previously only been found in several species of Proteobacteria and Campylobacterota, and the role of N-linked glycans in bacteria is still not fully understood. C. hutchinsonii has a unique cell-contact cellulose degradation mechanism, and many cell surface proteins including cellulases are secreted by the T9SS. Here, we found that C. hutchinsonii, a member of the phylum Bacteroidetes, has an N-glycosylation system. Glycosyltransferase CHU_3842 was found to participate in the N-glycosylation of C. hutchinsonii proteins, and had effects on cell resistance to some chemicals, cell motility, and cellulose degradation. Moreover, N-glycosylation occurs on the CTD translocation signal of T9SS. The glycosylation of CTD apears to play an important role in affecting T9SS substrates transportation and localization. This study enriched our understanding of the widespread existence and multiple biological roles of N-glycosylation in bacteria.

Translation Control of Swarming Proficiency in Bacillus subtilis by 5-Amino-pentanolylated Elongation Factor P

Elongation factor P (EF-P) accelerates diprolyl synthesis and requires a posttranslational modification to maintain proteostasis. Two phylogenetically distinct EF-P modification pathways have been described and are encoded in the majority of Gram-negative bacteria, but neither is present in Gram-positive bacteria. Prior work suggested that the EF-P-encoding gene (efp) primarily supports Bacillus subtilis swarming differentiation, whereas EF-P in Gram-negative bacteria has a more global housekeeping role, prompting our investigation to determine whether EF-P is modified and how it impacts gene expression in motile cells. We identified a 5-aminopentanol moiety attached to Lys(32) of B. subtilis EF-P that is required for swarming motility. A fluorescent in vivo B. subtilis reporter system identified peptide motifs whose efficient synthesis was most dependent on 5-aminopentanol EF-P. Examination of the B. subtilis genome sequence showed that these EF-P-dependent peptide motifs were represented in flagellar genes. Taken together, these data show that, in B. subtilis, a previously uncharacterized posttranslational modification of EF-P can modulate the synthesis of specific diprolyl motifs present in proteins required for swarming motility.