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ATPase activity of Mycobacterium tuberculosis SecA1 and SecA2 proteins and its importance for SecA2 function in

Jie M Hou1, Nadia G D'Lima, Nathan W Rigel

  • 1Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut 06269-3125, USA.

Journal of Bacteriology
|May 20, 2008
PubMed

Insights

Mycobacterium tuberculosis possesses two SecA proteins, SecA1 and SecA2. SecA2

Area of Science:

  • Microbiology
  • Molecular Biology
  • Biochemistry

Background:

  • The Sec-dependent pathway, utilizing SecA and SecYEG, is crucial for protein export in bacteria.
  • Pathogenic bacteria like Mycobacterium tuberculosis have two SecA homologs: SecA1 (essential) and SecA2 (virulence-associated).
  • The enzymatic functions of distinct SecA homologs within the same species remain largely undefined.

Purpose of the Study:

  • To investigate and compare the ATP-binding and enzymatic activities of Mycobacterium tuberculosis SecA1 and SecA2.
  • To determine the role of ATP binding in the function of the accessory SecA2 protein.

Main Methods:

  • Comparative analysis of ATP binding affinities for M. tuberculosis SecA1 and SecA2.
  • Site-directed mutagenesis of the conserved Walker A motif in SecA2 (K115R) to abolish ATP binding.
  • Assessment of the SecA2(K115R) mutant's effect on M. tuberculosis intracellular growth in macrophages.

Main Results:

  • Both M. tuberculosis SecA1 and SecA2 exhibit high-affinity ATP binding, with SecA2 showing stronger affinity than SecA1.
  • Mutating the conserved lysine in SecA2's Walker A motif (SecA2(K115R)) abrogated ATP binding.
  • The SecA2(K115R) variant failed to support M. tuberculosis intracellular growth in macrophages, highlighting the necessity of ATP binding for SecA2 function.

Conclusions:

  • This study provides the first evidence of ATPase activity in accessory SecA proteins.
  • ATP binding is essential for the virulence function of Mycobacterium tuberculosis SecA2.
  • The findings elucidate the functional significance of SecA2's enzymatic activity in bacterial pathogenesis.

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