MptpB, a virulence factor from Mycobacterium tuberculosis, exhibits triple-specificity phosphatase activity

Nicola Beresford, Sumayya Patel, Jane Armstrong, Balázs Szöor, Anthony P. Fordham-Skelton, Lydia Tabernero*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

Bacterial pathogens have developed sophisticated mechanisms of evading the immune system to survive in infected host cells. Central to the pathogenesis of Mycobacterium tuberculosis is the arrest of phagosome maturation, partly through interference with PtdIns signalling. The protein phosphatase MptpB is an essential secreted virulence factor in M. tuberculosis. A combination of bioinformatics analysis, enzyme kinetics and substrate-specificity characterization revealed that MptpB exhibits both dual-specificity protein phosphatase activity and, importantly, phosphoinositide phosphatase activity. Mutagenesis of conserved residues in the active site signature indicates a cysteine-based mechanism of dephosphorylation and identifies two new catalytic residues, Asp165, essential in catalysis, and Lys164, apparently involved in substrate specificity. Sequence similarities with mammalian lipid phosphatases and a preference for phosphoinositide substrates suggests a potential novel role of MptpB in PtdIns metabolism in the host and reveals new perspectives for the role of this phosphatase in mycobacteria pathogenicity.

Original languageEnglish
Pages (from-to)13-18
Number of pages6
JournalBiochemical Journal
Issue number1
Publication statusPublished - 15 Aug 2007

Keywords / Materials (for Non-textual outputs)

  • Bacterial phosphatase
  • Dual-specificity
  • Lipid phosphatase
  • Protein phosphatase
  • Signalling


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