IBR   13079
INSTITUTO DE BIOLOGIA MOLECULAR Y CELULAR DE ROSARIO
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Thermosensor DesK Measures Membrane Thickness
Autor/es:
CYBULSKI LARISA; DE MENDOZA DIEGO
Lugar:
Baltimore
Reunión:
Encuentro; 55th Annual Meeting Biophysical Society; 2011
Institución organizadora:
Biophysical Society
Resumen:
The bacterium Bacillus subtilis adjusts the composition of membrane lipids to
cope with temperature variations. The histidine kinase
DesK is a five-pass transmembrane thermosensor suited to remodel membrane
fluidity in Bacillus subtilis according to temperature. To understand
the mechanism of sensing, individual transmembrane segments (TMS) were fused to
the cytoplasmic catalytic domain of DesK (DesKC) and the ability to respond to
temperature analyzed. Surprisingly, a hybrid TMS composed of 17 aminoacids of
the first TMS and the C-terminal 14-residue portion of TM5 fused to DesKC, fully
retains in vivo and in vitro the sensing properties of full-length
DesK [1].
Besides, when TMS1-DesKC or TMS5-DesKC is expressed in vivo individually, they
are unresponsive to temperature. Nevertheless, when they are co-expressed
thermosensing is recovered; suggesting that interactions between TMS1 and TMS5
are needed for signaling.
The N-terminus of TMS1 contains three hydrophilic aminoacids near
the lipid-water interface creating an instability hot spot. We showed that 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 biochemical studies including in vitro reconstitution of the MS in liposomes with different chain
length.