Glutamine‐rich toxic proteins GrtA, GrtB and GrtC together with the antisense RNA AsgR constitute a toxin–antitoxin‐like system in Corynebacterium glutamicum

Abstract

The Corynebacterium glutamicum R grtA (cgR_2936), grtB (cgR_2934) and grtC (cgR_2933) genes were identified as paralogs encoding glutamine-rich toxic proteins. We also identified a new antisense small RNA AsgR (antisense sRNA for grtA) that overlaps the 3' end of the grtA gene. Single over-expressions of grtA, grtB and grtC resulted in complete inhibition of Escherichia coli cell growth. This growth was rescued by co-expression of AsgR. Similar effects were observed in C. glutamicum, although the toxicities of these proteins were moderate. Inhibition of AsgR transcription resulted in increased levels and prolonged half-lives of grtA, grtB and grtC mRNAs. We also found that the expression levels of grtA, grtB and grtC were increased in an RNase III deletion mutant. Primer extension analysis revealed the RNase III cleavage site to be in the 3' untranslated region (3'-UTR) of the grtA mRNA. The expression levels of grtA, grtB and grtC were increased after exposure to several stresses, including heat shock, treatment with penicillin G, lysozyme or H O . The deletions of grtABC and asgR genes resulted in decreased survival rate under several stresses. These results indicate that GrtABC and AsgR constitute a type I toxin-antitoxin-like system in C. glutamicum.

Targeting Iron - Respiratory Reciprocity Promotes Bacterial Death

“…Other downregulated categories include protein products necessary for electron transport or another part of the respiratory chain (CoxA, CoxB, EtfA, EtfB, FadH1, PA14_02460, PA14_06640, PA14_25840), fatty acid oxidation (FoaA, FoaB), antioxidants (GpO), methionine import (MetN1, MetQ-I), Mg 2+ transport (MgtA), molybdate ion transport (ModA), cell adhesion (Pa1L), biofilm formation (PfpL, PA14_34050), transcriptional regulation (PsrA, PA14_27530, PA14_40380), universal stress proteins (UspA, PA14_21220 [UspK], PA14_66460) and small molecule transport (PA14_34770). Among upregulated categories were genes coding for proteins necessary for amino acid transport (AroP2), sulfate transport (CysT; Figure S9 ), glutamine-rich toxic protein (GrtA; inhibits E. coli growth 71 ), molybdopterin cofactor biosynthesis (MoeA1, MoaB1), respiratory nitrate reductase (NarG, NarH, NarI, NarJ; Figure S9 ) responsible - together with molybdopterin cofactor - for anaerobic growth of P. aeruginosa in cystic fibrosis 72 , anaerobic regulation of denitrification (NosR; Figure S9 ), multidrug efflux (OprJ), cell wall biosynthesis (PbpA), sulfate binding or metabolism (SbP, SsuE; Figure S9 ), a sulfonate transporter (SsuA), a serine endopeptidase (PA14_24360; Figure S9 ), and a putative beta-lactamase (PA14_41280) that cleaves beta-lactam antibiotics to promote resistance 73 . We next compared (i-iii) data ( Figure S8C ) to appreciate changes common to both 5 and 20 µM N-104.…”

Type I Toxin-Antitoxin Systems in Clostridia

“…One hypothesis to explain the potential role of stress-induced type I TA modules in metabolic and stress adaptation in B. subtilis is the bacteriostasis induction helping dormant cells to cope with stresses [6,43]. A recently described type I TA-like system grtABC -AsgR is involved in the stress response in Corynebacterium glutamicum [90]. In C. difficile , the identification of Sigma B-dependent promoters upstream of type I toxin and antitoxin genes also suggests their potential role in stress response mechanisms in this pathogen [23,24].…”