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Loss of kinase activity in Mycobacterium tuberculosis multidomain protein Rv1364c

Preeti Sachdeva1, Azeet Narayan, Richa Misra

  • 1Institute of Genomics and Integrative Biology (CSIR), Delhi, India.

The FEBS Journal
|November 20, 2008
PubMed

Insights

Researchers identified a novel protein in Mycobacterium tuberculosis that integrates the entire regulatory pathway for sigma factor F (SigF). This protein, Rv1364c, and another, UsfX, show a loss of kinase activity, potentially explaining SigF regulation in this pathogen.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Biochemistry

Background:

  • Alternative sigma factors are crucial for bacterial gene regulation, controlled by complex phosphorylation cascades.
  • In Mycobacterium tuberculosis, the regulation of sigma factor F (SigF) involves anti-SigF and anti-anti-SigF proteins, but the kinases and phosphatases remain elusive.
  • Understanding these regulatory mechanisms is vital for deciphering bacterial adaptation and pathogenesis.

Purpose of the Study:

  • To identify and characterize the missing phosphorylation-dephosphorylation factors in the Mycobacterium tuberculosis SigF regulatory pathway.
  • To investigate the novel multidomain protein Rv1364c as a potential integrated regulator of SigF.
  • To elucidate the kinase activity of Rv1364c and UsfX in the context of SigF regulation.

Main Methods:

  • Sequence analysis of the Mycobacterium tuberculosis Rv1364c protein to predict functional domains (phosphatase, anti-SigF, anti-anti-SigF).
  • Biochemical assays using purified Rv1364c (RsbW domain) and UsfX proteins.
  • Assessment of autophosphorylation, phosphotransfer capabilities, and binding affinity to ATP analogs.

Main Results:

  • Rv1364c integrates phosphatase (RsbU), anti-SigF (RsbW), and anti-anti-SigF (RsbV) domains within a single polypeptide.
  • The RsbW domain of Rv1364c and the UsfX protein exhibit significant substitutions and deletions, leading to a loss of kinase activity and impaired ATP binding.
  • Despite reduced kinase function, Rv1364c and UsfX retain functional interactions with cognate sigma and anti-anti-sigma factors.

Conclusions:

  • The identified loss of kinase activity in Rv1364c and UsfX represents a critical missing link in the phosphorylation-dependent regulation of SigF in Mycobacterium tuberculosis.
  • Rv1364c acts as a unique, species-specific multidomain protein that likely orchestrates the entire SigF signal transduction cascade.
  • These findings provide new insights into the intricate regulatory networks governing bacterial gene expression and adaptation.

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