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Substrate-specific diffusion of select dicarboxylates through Chlamydia trachomatis PorB

A Kubo1, R S Stephens

  • 1Division of Infectious Diseases, School of Public Health, 140 Earl Warren Hall, University of California, Berkeley, CA 94720, USA.

Microbiology (Reading, England)
|November 9, 2001
PubMed

Insights

Chlamydial PorB is a dicarboxylate-specific porin, facilitating the uptake of 2-oxoglutarate. This transport is crucial for the incomplete tricarboxylic acid (TCA) cycle, enabling carbon and energy production in chlamydiae.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Biochemistry

Background:

  • Chlamydiae possess two outer membrane porins: MOMP and PorB.
  • MOMP acts as a general porin for various solutes like carbohydrates and amino acids.
  • PorB's limited general transport suggests a specialized role, potentially linked to the incomplete tricarboxylic acid (TCA) cycle requiring exogenous dicarboxylates like 2-oxoglutarate or glutamate.

Purpose of the Study:

  • To investigate the substrate specificity of the chlamydial PorB porin.
  • To determine if PorB facilitates the transport of molecules essential for the chlamydial TCA cycle.

Main Methods:

  • Utilized a liposome-swelling assay to assess anion diffusion.
  • Employed an enzyme-linked liposome assay to quantify transport.
  • Focused on the diffusion of dicarboxylates, specifically 2-oxoglutarate, through PorB.

Main Results:

  • Demonstrated efficient diffusion of dicarboxylates, including 2-oxoglutarate, through the PorB porin.
  • Confirmed PorB's role as a specific transporter for these dicarboxylates.
  • Established that PorB efficiently transports substrates required by the chlamydial TCA cycle.

Conclusions:

  • PorB functions as a dicarboxylate-specific porin in Chlamydiae.
  • This specificity allows for the acquisition of essential intermediates for the incomplete TCA cycle.
  • PorB plays a vital role in chlamydial carbon and energy metabolism by importing key metabolites.

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