title: A lipid-mediated conformational switch modulates the thermosensing activity of DesK.
abstract: The thermosensor DesK is a multipass transmembrane histidine-kinase that allows the bacterium Bacillus subtilis to adjust the levels of unsaturated fatty acids required to optimize membrane lipid fluidity. The cytoplasmic catalytic domain of DesK behaves like a kinase at low temperature and like a phosphatase at high temperature. Temperature sensing involves a built-in instability caused by a group of hydrophilic residues located near the N terminus of the first transmembrane (TM) segment. These residues are buried in the lipid phase at low temperature and partially "buoy" to the aqueous phase at higher temperature with the thinning of the membrane, promoting the required conformational change. Nevertheless, the core question remains poorly understood: How is the information sensed by the transmembrane region converted into a rearrangement in the cytoplasmic catalytic domain to control DesK activity? Here, we identify a "linker region" (KSRKERERLEEK) that connects the TM sensor domain with the cytoplasmic catalytic domain involved in signal transmission. The linker adopts two conformational states in response to temperature-dependent membrane thickness changes: (i) random coiled and bound to the phospholipid head groups at the water-membrane interface, promoting the phosphatase state or (ii) unbound and forming a continuous helix spanning a region from the membrane to the cytoplasm, promoting the kinase state. Our results uphold the view that the linker is endowed with a helix/random coil conformational duality that enables it to behave like a transmission switch, with helix disruption decreasing the kinase/phosphatase activity ratio, as required to modulate the DesK output response.
authors: Instituto de Biología Molecular y Celular de Rosario-Consejo Nacional de Investigaciones Científicas y Técnicas de Argentina (CONICET) and Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Ocampo y Esmeralda, Predio CONICET, S2000FHQ Rosario, Argentina.
authors: María Eugenia
authors: ME
authors: Inda
authors: Michel
authors: M
authors: Vandenbranden
authors: Ariel
authors: A
authors: Fernández
authors: Diego
authors: D
authors: de Mendoza
authors: Jean-Marie
authors: JM
authors: Ruysschaert
authors: Larisa Estefanía
authors: LE
authors: Cybulski
mesh_terms: D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000235:genetics / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli; D000071677:Histidine Kinase; D013058:Mass Spectrometry; D008560:Membrane Fluidity / Q000502:physiology*; D008565:Membrane Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011487:Protein Conformation; D011494:Protein Kinases / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D013697:Thermosensing / Q000235:genetics / Q000502:physiology*
chemical_list: D008565:Membrane Proteins; D011494:Protein Kinases; D000071677:Histidine Kinase
keywords: membrane–protein interaction; sensor biophysics; signal transduction; two-component system