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Rv1698 of Mycobacterium tuberculosis represents a new class of channel-forming outer membrane proteins

Axel Siroy1, Claudia Mailaender, Daniel Harder

  • 1Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA.

The Journal of Biological Chemistry
|April 25, 2008
PubMed

Insights

Rv1698 is a newly discovered channel protein in Mycobacterium tuberculosis outer membranes. This protein facilitates nutrient transport and represents a new class of mycobacterial outer membrane proteins.

Area of Science:

  • Microbiology
  • Structural Biology
  • Biophysics

Background:

  • Mycobacteria possess a unique outer membrane rich in mycolic acids, crucial for virulence.
  • OmpA is the only known channel-forming protein in the Mycobacterium tuberculosis outer membrane.
  • Rv1698, a predicted outer membrane protein, had an unknown function.

Purpose of the Study:

  • To investigate the function of the Rv1698 protein in Mycobacterium tuberculosis.
  • To determine if Rv1698 forms channels in the mycobacterial outer membrane.
  • To characterize the properties of Rv1698 channels.

Main Methods:

  • Functional complementation assays in a Mycobacterium smegmatis porin mutant.
  • Nutrient uptake experiments.
  • Lipid bilayer reconstitution and single-channel electrophysiology.
  • Proteinase K accessibility assays.

Main Results:

  • Rv1698 expression restored antibiotic sensitivity and partially complemented glucose uptake defects in M. smegmatis.
  • Purified Rv1698 formed channels in lipid bilayers with a conductance of 4.5 nS (1 M KCl) and weak cation preference.
  • Rv1698 was shown to be surface-accessible on recombinant M. smegmatis.

Conclusions:

  • Rv1698 functions as an unspecific channel protein in the Mycobacterium tuberculosis outer membrane.
  • Rv1698 likely facilitates transport across the mycobacterial outer membrane.
  • Rv1698 represents the first identified member of a novel class of channel proteins specific to mycolic acid-containing membranes.

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