Membrane Transport | Potassium Channels in the Inner Membrane of Mitochondria in Various Organisms: From Unicellular Eukaryotes to Higher Plants and Mammals

Cell walls of bacteria of the genera Mycobacterium and Corynebacterium contain high levels of (coryno)mycolic acids. These very long chain fatty acids are synthesized on the cytoplasmic leaflet of the inner membrane (IM) prior to conjugation to the disaccharide, trehalose, and transport to the periplasm. Recent studies on Corynebacterium glutamicum have shown that acetylation of trehalose monohydroxycorynomycolate (hTMCM) promotes its transport across the inner membrane. Acetylation is mediated by the membrane acetyltransferase, TmaT, and is dependent on the presence of a putative methyltransferase, MtrP. Here, we identify a third protein that is required for the acetylation and membrane transport of hTMCM. Deletion of the C. glutamicum gene NCgl2761 (Rv0226c in Mycobacterium tuberculosis) abolished synthesis of acetylated hTMCM (AcTMCM), resulting in an accumulation of hTMCM in the inner membrane and reduced synthesis of trehalose dihydroxycorynomycolate (h2TDCM), a major outer membrane glycolipid. Complementation with the NCgl2761 gene, designated here as mmpA, restored the hTMCM:h2TDCM ratio. Comprehensive lipidomic analysis of the ΔtmaT, ΔmtrP and ΔmmpA mutants revealed strikingly similar global changes in overall membrane lipid composition. Our findings suggest that the acetylation and membrane transport of hTMCM is regulated by multiple proteins: MmpA, MtrP and TmaT, and that defects in this process lead to global, potentially compensatory changes in the composition of inner and outer membranes.

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Plasma membrane transport systems in higher plants: From black boxes to molecular physiology

Physiologia Plantarum ◽

10.1111/j.1399-3054.1997.tb03450.x ◽

1997 ◽

Vol 100 (1) ◽

pp. 1-15 ◽

Cited By ~ 26

Author(s):

Helen Logan ◽

Mireille Basset ◽

Anne-Alienor Very ◽

Herve Sentenac

Keyword(s):

Plasma Membrane ◽

Membrane Transport ◽

Higher Plants ◽

Transport Systems ◽

Molecular Physiology ◽

Black Boxes ◽

Membrane Transport Systems

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Anionic lipids and the cytoskeletal proteins MreB and RodZ define the spatio-temporal distribution and function of membrane stress controller PspA in Escherichia coli

Microbiology ◽

10.1099/mic.0.078527-0 ◽

2014 ◽

Vol 160 (11) ◽

pp. 2374-2386 ◽

Cited By ~ 15

Author(s):

Goran Jovanovic ◽

Parul Mehta ◽

Liming Ying ◽

Martin Buck

Keyword(s):

Escherichia Coli ◽

Higher Plants ◽

Cell Envelope ◽

Membrane Integrity ◽

Temporal Distribution ◽

Cytoskeletal Proteins ◽

Dual Function ◽

Membrane Stress ◽

Inner Membrane ◽

Anionic Lipids

All cell types must maintain the integrity of their membranes. The conserved bacterial membrane-associated protein PspA is a major effector acting upon extracytoplasmic stress and is implicated in protection of the inner membrane of pathogens, formation of biofilms and multi-drug-resistant persister cells. PspA and its homologues in Gram-positive bacteria and archaea protect the cell envelope whilst also supporting thylakoid biogenesis in cyanobacteria and higher plants. In enterobacteria, PspA is a dual function protein negatively regulating the Psp system in the absence of stress and acting as an effector of membrane integrity upon stress. We show that in Escherichia coli the low-order oligomeric PspA regulatory complex associates with cardiolipin-rich, curved polar inner membrane regions. There, cardiolipin and the flotillin 1 homologue YqiK support the PspBC sensors in transducing a membrane stress signal to the PspA-PspF inhibitory complex. After stress perception, PspA high-order oligomeric effector complexes initially assemble in polar membrane regions. Subsequently, the discrete spatial distribution and dynamics of PspA effector(s) in lateral membrane regions depend on the actin homologue MreB and the peptidoglycan machinery protein RodZ. The consequences of loss of cytoplasmic membrane anionic lipids, MreB, RodZ and/or YqiK suggest that the mode of action of the PspA effector is closely associated with cell envelope organization.

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