Membrane thickness cue for cold sensing in a bacterium.
Thermosensors are ubiquitous integral membrane proteins found in all kinds of life. They are involved in many physiological roles, including membrane remodeling, chemotaxis, touch, and pain [1-3], but, the mechanism by which their transmembrane (TM) domains transmit temperature signals is largely unknown. The histidine kinase DesK from Bacillus subtilis is the paradigmatic example of a membrane-bound thermosensor suited to remodel membrane fluidity when the temperature drops below approximately 30°C [1, 4] providing, thus, a tractable system for investigating the mechanism of TM-mediated input-output control of thermal adaptation. Here we show that the multimembrane-spanning domain from DesK can be simplified into a chimerical single-membrane-spanning minimal sensor (MS) that fully retains, in vivo and in vitro, the sensing properties of the parental system. The MS N terminus contains three hydrophilic amino acids near the lipid-water interface creating an instability hot spot. Mutational analysis of this boundary-sensitive beacon revealed that membrane thickness controls the signaling state of the sensor by dictating the hydration level of the metastable hydrophilic spot. Guided by these results we biochemically demonstrated that the MS signal transmission activity is sensitive to bilayer thickness. Membrane thickness could be a general cue for sensing temperature in many organisms.
Cybulski
Larisa E
LE
Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET) and Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, Rosario, Argentina. cybulski@ibr.gov.ar
Martín
Mariana
M
Mansilla
María C
MC
Fernández
Ariel
A
de Mendoza
Diego
D
D000595:Amino Acid Sequence; D001412:Bacillus subtilis / Q000502:physiology*; D001426:Bacterial Proteins / Q000737:chemistry / Q000502:physiology*; D002462:Cell Membrane; D003080:Cold Temperature; D000071677:Histidine Kinase; D008565:Membrane Proteins / Q000737:chemistry / Q000502:physiology*; D008969:Molecular Sequence Data; D010766:Phosphorylation; D017354:Point Mutation; D011494:Protein Kinases / Q000737:chemistry / Q000502:physiology
D001426:Bacterial Proteins; D008565:Membrane Proteins; D011494:Protein Kinases; D000071677:Histidine Kinase