The Single Transmembrane Segment of Minimal Sensor DesK Senses Temperature via a Membrane-Thickness Caliper

DE MENDOZA, DIEGO; OLIVEIRA, R. G.; INDA, M. E. ; CYBULSKI, LARISA E.; DE MENDOZA, DIEGO; OLIVEIRA, R. G.; INDA, M. E. ; CYBULSKI, LARISA E.

JOURNAL OF BACTERIOLOGY

AMER SOC MICROBIOLOGY

Lugar: Washington; Año: 2016 vol. 198 p. 2945 - 2954

0021-9193

Thermosensors detect temperature changes and trigger cellular responses crucial for survival at different temperatures. Thethermosensor DesK is a transmembrane (TM) histidine kinase which detects a decrease in temperature through its TM segments(TMS). Here, we address a key issue: how a physical stimulus such as temperature can be converted into a cellular response. Weshow that the thickness of Bacillus lipid membranes varies with temperature and that such variations can be detected by DesKwith great precision. On the basis of genetic studies and measurements of in vitro activity of a DesK construct with a single TMS(minimal sensor DesK [MS-DesK]), reconstituted in liposomes, we propose an interplay mechanism directed by a conserveddyad, phenylalanine 8-lysine 10. This dyad is critical to anchor the only transmembrane segment of the MS-DesK construct tothe extracellular water-lipid interphase and is required for the transmembrane segment of MS-DesK to function as a caliper forprecise measurement of membrane thickness. The data suggest that positively charged lysine 10, which is located in the hydrophobiccore of the membrane but is close to the water-lipid interface, pulls the transmembrane region toward the water phase tolocalize its charge at the interface. Nevertheless, the hydrophobic residue phenylalanine 8, located at the N-terminal extreme ofthe TMS, has a strong tendency to remain in the lipid phase, impairing access of lysine 10 to the water phase. The outcome of thisinterplay is a fine-tuned sensitivity to membrane thickness that elicits conformational changes that favor different signalingstates of the protein.