VapC proteins from Mycobacterium tuberculosis share ribonuclease sequence specificity but differ in regulation and toxicity

Abstract

The chromosome of Mycobacterium tuberculosis (Mtb) contains a large number of Type II toxin-antitoxin (TA) systems. The majority of these belong to the VapBC TA family, characterised by the VapC protein consisting of a PIN domain with four conserved acidic residues, and proposed ribonuclease activity. Characterisation of five VapC (VapC1, 19, 27, 29 and 39) proteins from various regions of the Mtb chromosome using a combination of pentaprobe RNA sequences and mass spectrometry revealed a shared ribonuclease sequence-specificity with a preference for UAGG sequences. The TA complex VapBC29 is auto-regulatory and interacts with inverted repeat sequences in the vapBC29 promoter, whereas complexes VapBC1 and VapBC27 display no auto-regulatory properties. The difference in regulation could be due to the different properties of the VapB proteins, all of which belong to different VapB protein families. Regulation of the vapBC29 operon is specific, no cross-talk among Type II TA systems was observed. VapC29 is bacteriostatic when expressed in Mycobacterium smegmatis, whereas VapC1 and VapC27 displayed no toxicity upon expression in M. smegmatis. The shared sequence specificity of the five VapC proteins characterised is intriguing, we propose that the differences observed in regulation and toxicity is the key to understanding the role of these TA systems in the growth and persistence of Mtb.

Depletion of the DarG antitoxin in Mycobacterium tuberculosis triggers the DNA‐damage response and leads to cell death

“…In contrast, most other toxins studied in Mtb exert a bacteriostatic effect (Singh et al, 2010;Tiwari et al, 2015;Agarwal et al, 2018;Sharrock et al, 2018;Tandon et al, 2019). This suggests that, among…”

“…Activation of DarT Mtb has a bactericidal effect (Figure 3b), similar to induction of MbcT, the toxin of the only other characterized TA system in Mtb harboring an essential antitoxin (Freire et al ., 2019). In contrast, most other toxins studied in Mtb exert a bacteriostatic effect (Singh et al ., 2010; Tiwari et al ., 2015; Agarwal et al ., 2018; Sharrock et al ., 2018; Tandon et al ., 2019). This suggests that, among TA systems, DarG Mtb may be an attractive drug target.…”

Innate Immune Responses of Galleria mellonella to Mycobacterium bovis BCG Challenge Identified Using Proteomic and Molecular Approaches

“…At 4 h pi, proteins were associated with metabolic changes. These included: ribonuclease VapC and 2,3 bisphosphoglycerate-dependent phosphoglycerate mutase, both of which have been associated with regulation of metabolism in response to intracellular conditions and glucogenesis ( Hillion et al., 2017 ; Sharrock et al., 2018 ). Adenosylhomocysteinase catalyses the reversible processing of S-adenosylmethionine dependent methyltransferase reaction and is essential for in vitro growth, and was upregulated in lung tissues of MTB infected mice ( Singhal et al., 2012 ).…”

PhoH2 proteins couple RNA helicase and RNAse activities

“…In this case, VapC regulates the rate of glycerol utilization, linking the anabolic and catabolic demands of the cell to posttranscriptionally tune catabolic metabolism . VapC proteins VapC1, VapC29, and VapC27 from M. tuberculosis , like VapC from M. smegmatis also cleave RNA at specific sites …”