A 2-helix coiled-coil controls the activities of DesK, a bacterial thermosensor

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

Congreso; 50th Annual Meeting Argentine Society for Biochemistry and Molecular Biology; 2014

DesK, a histidine kinase from Bacillus subtilis, is a membrane-bound thermosensor suited to remodel membrane fluidity when the temperature drops below~30°C. This sensor protein behaves as a kinase at cold temperatures, promoting the phosphorylation of its cognate response regulator DesR, which in turns activates the transcription of des, coding for the acyl-lipid desaturase Δ5-Des. Promotion of membrane fluidity by 5-Des switches DesK from kinase to a phosphatase, shutting down the expression of the desaturase. Recently, our group reported the crystal structures of the cytoplasmic region of DesK in three different functional states. Analysis of these structures prompted us to construct a set of mutants and determine, through in vivo and in vitro experiments, the crucial role of the N-terminal 2-helix coiled coil (2-HCC) that links the sensing and catalytic domains, in controlling the phosphatase/kinase output activity. In addition, molecular dynamics simulations strongly support the experimental data, and remark hydration as a key player in the structural changes linked to activity modulation. Altogether, our results highlight the 2-HCC as an essential structural element in the control of the activity of the thermosensor DesK.