Transmembrane prolines mediate signal sensing and decoding in Bacillus subtilis DesK histidine kinase
Fecha
2019-11-26
Título de la revista
ISSN de la revista
Título del volumen
Editor
American Society for Microbiology
Resumen
Descripción
Environmental awareness is an essential attribute of all organisms. The
homeoviscous adaptation system of Bacillus subtilis provides a powerful experimen tal model for the investigation of stimulus detection and signaling mechanisms at
the molecular level. These bacteria sense the order of membrane lipids with the
transmembrane (TM) protein DesK, which has an N-terminal sensor domain and an
intracellular catalytic effector domain. DesK exhibits autokinase activity as well as
phosphotransferase and phosphatase activities toward a cognate response regulator,
DesR, that controls the expression of an enzyme that remodels membrane fluidity
when the temperature drops below 30°C. Membrane fluidity signals are transmit ted from the DesK sensor domain to the effector domain via rotational movements
of a connecting 2-helix coiled coil (2-HCC). Previous molecular dynamic simulations
suggested important roles for TM prolines in transducing the initial signals of mem brane fluidity status to the 2-HCC. Here, we report that individual replacement of
prolines in DesKs TM1 and TM5 helices by alanine (DesKPA) locked DesK in a
phosphatase-ON state, abrogating membrane fluidity responses. An unbiased muta genic screen identified the L174P replacement in the internal side of the repeated
heptad of the 2-HCC structure that alleviated the signaling defects of every trans membrane DesKPA substitution. Moreover, substitutions by proline in other internal
positions of the 2-HCC reestablished the kinase-ON state of the DesKPA mutants.
These results imply that TM prolines are essential for finely tuned signal generation
by the N-terminal sensor helices, facilitating a conformational control by the meta stable 2-HCC domain of the DesK signaling state.
Palabras clave
Histidine Kinase, Proline, Thermosensing, Two-component Regulatory Systems