Substrate-specific diffusion of select dicarboxylates through Chlamydia trachomatis PorB.
Chlamydiae contain two porins, MOMP and PorB, that facilitate diffusion of solutes through the outer membrane. MOMP is a general porin that permits the diffusion of a wide variety of compounds including carbohydrates and amino acids. The relative inefficiency of PorB as a general porin and its low abundance in the outer membrane suggest that it may function as a substrate-specific porin. The tricarboxylic acid (TCA) cycle of chlamydiae is incomplete and to function would require the exogenous acquisition of 2-oxoglutarate or glutamate. A liposome-swelling assay for anions as well as an enzyme-linked liposome assay were used to demonstrate the efficient diffusion of dicarboxylates such as 2-oxoglutarate through PorB. These data demonstrate that PorB is a dicarboxylate-specific porin that may feed the chlamydial TCA cycle and provide chlamydiae with carbon and energy production intermediates.
Kubo
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Division of Infectious Diseases, School of Public Health, 140 Earl Warren Hall, University of California, Berkeley, CA 94720, USA.
Stephens
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D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport; D002244:Carbon / Q000378:metabolism; D002463:Cell Membrane Permeability; D002692:Chlamydia trachomatis / Q000235:genetics / Q000378:metabolism*; D002952:Citric Acid Cycle / Q000502:physiology; D018272:Porins / Q000235:genetics / Q000378:metabolism*
D001425:Bacterial Outer Membrane Proteins; D018272:Porins; C057699:porin protein, Neisseria; C071677:omp1 protein, Chlamydia trachomatis; D002244:Carbon