Temperature Sensing by Membranes

EMILIO SAITA; DANIELA ALBANESI; LUCIANO ABRIATA; MATTEO DAL PERARO; DIEGO DE MENDOZA

Aberdeen

Congreso; 55th International Conference on the Biosciences of Lipids: Lipids as Mediators of Health and Disease; 2014

ICBL

Bacteria are capable to regulate the membrane fluidity in order to survive and continue growth while exposed to temperatures below those of their normal conditions. In this process, membrane fluidity is reestablished by desaturation of the acyl chain of membrane phospholipids. In Bacillus subtilis, the model of Gram-positive bacteria, the transcription of the gen des, coding for an acyl lipid desaturase, is controlled by a thermosensor that senses changes in the membrane properties due to abrupt temperature change. This thermosensor, named DesK, is a bifunctional histidin kinase/phosphatase that senses membrane biophysical state of the membrane and transmits this signal to the transcriptional apparatus. Several experiments, in vivo and in vitro, on DesK mutants allowed to establish the transmembrane domain (TM) as the responsible for signal sensing, and the cytoplasmatic domain (DesKC) as the responsible for signal transduction via phosphorylation of the associated response regulator (DesR). While DesKC alone (without TM) is soluble and has been crystalized in three different conformations associated with its catalytic states, little is known of the mechanism employed by the TM domain to detect the cold signal and control the catalytic state adopted by DesKC. Based on several in vivo and in vitro studies, complemented by analysis of DesKC crystallographic structures and supportive computational simulations, we propose a a model for signal transmission in wich incoming cold signals are transmitted through reversible stabilization/destabilization of a 2-helix parallel coiled-coil connecting the TM segments with the effector domain.