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Review
. 2004 Oct;186(20):6681-8.
doi: 10.1128/JB.186.20.6681-6688.2004.

Control of membrane lipid fluidity by molecular thermosensors

María C Mansilla  1 , Larisa E Cybulski, Daniela Albanesi, Diego de Mendoza
Affiliations
Review

Control of membrane lipid fluidity by molecular thermosensors

María C Mansilla et al. J Bacteriol. 2004 Oct.
No abstract available

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Figures

FIG. 1.
FIG. 1.
UFA biosynthesis in E. coli and B. subtilis. (A) In E. coli, FabA catalyzes the key step in UFA production, introducing the double bond into the acyl chain at the 10-carbon intermediate. FabA is a bifunctional enzyme that catalyzes both the removal of water to generate trans-2-decenoyl-ACP and the isomerization of this intermediate to cis-3-decenol-ACP. The FabB enzyme is required for the elongation of these unsaturated acyl-ACP intermediates, and FabF participates in SFA synthesis and in the elongation of 16:1 Δ9 palmitoleoyl-ACP to 18:1 Δ11 cis-vaccenoyl-ACP. The reactivity of this enzyme toward 16:1 Δ9 palmitoleoyl-ACP is increased after a temperature (temp) downshift. (B) Reactants and products of a representative fatty acid desaturase reaction. This is a 2e−- and O2-dependent dehydrogenation at an unactivated position of the fatty acyl chain, resulting in cis-double-bond formation. For stearoyl-CoA desaturase from mycobacteria (49), R is CoA; for acyl lipid desaturases from Bacillus (1, 32) and cyanobacteria (50), R is a phospholipid.
FIG. 2.
FIG. 2.
Branched-chain fatty acid biosynthesis in B. subtilis. Branched-chain amino acids are converted to branched-chain 2-keto-acid by a branched-chain amino acid transaminase (BCAT). Acyl-CoA intermediates are then synthesized by a branched-chain α-ketoacid dehydrogenase complex (BCKAD). Isovaleryl-CoA, isobutyryl-CoA, and 2-methylbutyryl-CoA are substrates of the fatty acid synthase (FAS II), yielding iso-branched-chain C15:0 and C17:0, iso-branched-chain C14:0 and C16:0, and anteiso-branched-chain C15:0 and C17:0 fatty acids, respectively. α-KG, α-ketoglutarate; Glt, glutamate.
FIG. 3.
FIG. 3.
Signal transduction pathway leading to membrane fluidity optimization in B. subtilis. It is proposed that DesK could assume different signaling states in response to changes in membrane fluidity. This is accomplished by regulating the ratio of kinase activity to phosphatase activity. (A) A phosphatase-dominant state is present when membrane lipids are disordered. (B) A kinase-dominant state of DesK predominates upon an increase in the proportion of ordered membrane lipids. This could be accomplished either after a sudden drop in temperature, which results in a drastic reduction in membrane fluidity regardless of the availability of anteiso-branched-chain fatty acid precursors (ABFP), or at 37°C when cells are growing in a medium devoid of ABFP. DesK-mediated phosphorylation of DesR results in transcriptional activation of des. (C) Activation of des results in synthesis of Des, which desaturates the acyl chains of membrane phospholipids. These newly synthesized UFAs inhibit des transcription by favoring the dephosphorylation of DesR.
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References

    1. Aguilar, P. S., J. E. Cronan, Jr., and D. de Mendoza. 1998. A Bacillus subtilis gene induced by cold shock encodes a membrane phospholipid desaturase. J. Bacteriol. 180:2194-2200. . - PMC - PubMed
    1. Aguilar, P. S., P. López, and D. de Mendoza. 1999. Transcriptional control of the low-temperature-inducible des gene, encoding the delta 5 desaturase of Bacillus subtilis. J. Bacteriol. 181:7028-7033. - PMC - PubMed
    1. Aguilar, P. S., A. M. Hernandez-Arriaga, L. E. Cybulski, A. C. Erazo, and D. de Mendoza. 2001. Molecular basis of thermosensing: a two-component signal transduction thermometer in Bacillus subtilis. EMBO J. 20:1681-1691. - PMC - PubMed
    1. Albanesi, D., M. C. Mansilla, and D. de Mendoza. 2004. The membrane fluidity sensor DesK of Bacillus subtilis controls the signal decay of its cognate response regulator. J. Bacteriol. 186:2655-2663. - PMC - PubMed
    1. Allen, E. E., and D. H. Bartlett. 2000. FabF is required for piezoregulation of cis-vaccenic acid levels and piezophilic growth of the deep-sea bacterium Photobacterium profundum strain SS9. J. Bacteriol. 182:1264-1271. - PMC - PubMed

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