Molecular logic of cold sensing

CYBULSKI, LARISA E, FERNÁNDEZ ARIEL, DE MENDOZA, DIEGO.

Salta

Congreso; Latina American Protein Society Meeting; 2010

Sociedad Argentina Biofísica

Molecular logic of cold sensing The soil bacterium Bacillus subtilis adjusts the composition of membrane lipids to cope with temperature variations. The thermosensor DesK is a membrane protein that controls the expression of the delta-5 desaturase by regulating the level of phosphorylation of the response regulator DesR. Progressive deletions of TM segments revealed that only the first TM segment (TM1) is essential to regulate the kinase activity.  Therefore, we re-engineered the 5 TMS domain of the DesK into a single-TMS chimeric sensor by combining the N-terminal 17-residue portion of TM1 with the C-terminal 14-residue portion of TM5, which is naturally fused to the cytosolic catalytic domain. This so-called Minimal Sensor (MS), with a unique TMS, fully retains in vivo and in vitro the sensing input and transmission output of the parental system. The MS N-terminus contains three hydrophilic aminoacids near the lipid-water interface creating an instability hot spot. This boundary-sensitive motif controls the sensing and transmission activity. Accordingly, we hypothesize that membrane thickness is the temperature agent that determines the signaling state of the cold sensor by dictating the hydration level of the meta-stable hydrophilic spot. This hypothesis is supported through the study of the signaling behavior of MS variants and biochemical studies including in vitro reconstitution of the MS in liposomes with different chain length. Membrane thickness could be a general cue for sensing temperature in many organisms.