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

PLoS One. 2018 Aug 31;13(8):e0203412. doi: 10.1371/journal.pone.0203412. eCollection 2018.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antitoxins / genetics
  • Bacterial Proteins / genetics*
  • Bacterial Toxins / genetics*
  • DNA-Binding Proteins / genetics
  • Gene Expression Regulation, Bacterial / genetics
  • Mycobacterium smegmatis / genetics
  • Mycobacterium tuberculosis / genetics*
  • Operon / genetics
  • Promoter Regions, Genetic / genetics
  • Ribonucleases / genetics*

Substances

  • Antitoxins
  • Bacterial Proteins
  • Bacterial Toxins
  • DNA-Binding Proteins
  • Ribonucleases

Grants and funding

VAA received funding from the New Zealand Royal Society, Te Aparangi, Marsden Fund, grant number: 10-UOW-091, https://www.royalsociety.org.nz/what-we-do/funds-and-opportunities/marsden/marsden-fund-standard/. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.