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Mycobacterial polyketide-associated proteins are acyltransferases: proof of principle with Mycobacterium tuberculosis

Kenolisa C Onwueme1, Julian A Ferreras, John Buglino

  • 1Department of Microbiology and Immunology, Weill Medical College of Cornell University, New York, NY 10021, USA.

Proceedings of the National Academy of Sciences of the United States of America
|April 9, 2004
PubMed

Insights

Mycobacterium tuberculosis (Mt) utilizes the PapA5 enzyme to synthesize complex lipids called phthiocerol dimycocerosate esters (PDIMs), which are crucial for virulence. This study functionally characterizes PapA5 as an acyltransferase essential for PDIM production.

Area of Science:

  • Microbiology
  • Biochemistry
  • Lipid Metabolism

Background:

  • Mycobacterium tuberculosis (Mt) produces virulence-associated lipids, including phthiocerol and phthiodiolone dimycocerosate esters (PDIMs).
  • The precise enzymatic mechanisms for PDIM synthesis in Mt are not fully elucidated.
  • Polyketide-associated proteins (Paps) are encoded within lipid synthesis gene clusters, but their functions are often uncharacterized.

Purpose of the Study:

  • To functionally characterize the polyketide-associated protein PapA5 from Mycobacterium tuberculosis.
  • To determine the role of PapA5 in the synthesis of PDIMs.
  • To investigate the potential acyltransferase activity of PapA5.

Main Methods:

  • Sequence analysis of PapA5 and its homologs.
  • Expression and purification of recombinant PapA5 protein.
  • In vitro enzymatic assays to assess acyltransferase activity.
  • Gene deletion analysis in Mycobacterium tuberculosis to evaluate the necessity of papA5 for PDIM synthesis.

Main Results:

  • Sequence analysis suggested PapA5 belongs to a subfamily of acyltransferases.
  • Recombinant PapA5 protein demonstrated confirmed acyltransferase activity.
  • Deletion of the papA5 gene in Mt abolished PDIM synthesis.
  • PapA5 is proposed to catalyze the diesterification of phthiocerol and phthiodiolone with mycocerosate.

Conclusions:

  • PapA5 is a crucial acyltransferase essential for the synthesis of phthiocerol dimycocerosate esters (PDIMs) in Mycobacterium tuberculosis.
  • The functional characterization of PapA5 provides insights into the biosynthesis of complex lipids in Mt.
  • Understanding PapA5 function may inform strategies targeting virulence and potentially lead to new insights into the synthesis of other complex lipids, such as those involved in rifamycin production.

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