Activation of the termosensor DesK involves reversible formation of a transmembrane serine zipper (este trabajo completo está en revisión en PNAS)

CYBULSKI LARISA ESTEFANÍA; JOOST BALLERING; ANASTASSIIA MOUSSATOVA; INDA, MARÍA EUGENIA;; DE MENDOZA DIEGO; KILLIAN ANTOINETTE

Rosario-Santa Fe

Congreso; Congreso 50 años de la Sociedad Argentina de Investigaciones Bioquímicas y Biología Molecular; 2014

Sociedad Argentina de Investigaciones Bioquímicas y Biología Molecular

DesK is a bacterial thermosensor involved in maintaining membrane fluidity in response to changes in environmental temperature. Here we aimed to elucidate the mode of action of DesK by studying a chimerical minimal sensor-DesK (MS-DesK), in which sensing and signaling are captured in a single transmembrane segment. This simplified version of the sensor allows investigating how membrane properties modulate protein activity by using synthetic peptides, corresponding to the membrane spanning parts of functional and non-functional mutants of MS-DesK incorporated in different lipid bilayers. The behavior of the peptides was investigated by circular dichroism, tryptophan fluorescence, in vitro activity and molecular modeling. Based on the results we constructed a working model for the mode of action of DesK, which was then tested in vivo with functional studies on MS-DesK mutants. The results suggest a new mechanism for sensing in which the protein responds to an increase in bilayer thickness by incorporation of a C-terminal hydrophilic motif at the intracellular water-lipid interface. Elongation of the transmembrane segment results in the exposure of three serines on the same side of the transmembrane helix to form a serine zipper motif. This switches the dimerization interface of the transmembrane segment of MS-DesK resulting in activation of the kinase state of DesK.