Interhelical H-Bonds Modulate the Activity of a Polytopic Transmembrane Kinase.

DesK is a Histidine Kinase that allows to maintain lipid homeostasis in response to changes in the environment. It is located in the membrane, and has five transmembrane helices and a cytoplasmic catalytic domain. The transmembrane region triggers the phosphorylation of the catalytic domain as soon as the membrane lipids rigidify.

A Transmembrane Histidine Kinase Functions as a pH Sensor.

The two-component system DesK-DesR regulates the synthesis of unsaturated fatty acids in the soil bacteria . This system is activated at low temperature and maintains membrane lipid fluidity upon temperature variations. Here, we found that DesK-the transmembrane histidine kinase-also responds to pH and studied the mechanism of pH sensing.

Driving the catalytic activity of a transmembrane thermosensor kinase.

DesK is a Bacillus thermosensor kinase that is inactive at high temperatures but turns activated when the temperature drops below 25 °C. Surprisingly, the catalytic domain (DesKC) lacking the transmembrane region is more active at higher temperature, showing an inverted regulation regarding DesK. How does the transmembrane region control the catalytic domain, repressing activity at high temperatures, but allowing activation at lower temperatures? By designing a set of temperature minimized sensors that share the same catalytic cytoplasmic domain but differ in number and position of hydrogen-bond (H-bond) forming residues along the transmembrane helix, we are able to tune, invert or disconnect activity from the input signal.

Activation of the bacterial thermosensor DesK involves a serine zipper dimerization motif that is modulated by bilayer thickness.

DesK is a bacterial thermosensor protein involved in maintaining membrane fluidity in response to changes in environmental temperature. Most likely, the protein is activated by changes in membrane thickness, but the molecular mechanism of sensing and signaling is still poorly understood. Here we aimed to elucidate the mode of action of DesK by studying the so-called "minimal sensor DesK" (MS-DesK), in which sensing and signaling are captured in a single transmembrane segment.

A lipid-mediated conformational switch modulates the thermosensing activity of DesK.

The thermosensor DesK is a multipass transmembrane histidine-kinase that allows the bacterium Bacillus subtilis to adjust the levels of unsaturated fatty acids required to optimize membrane lipid fluidity. The cytoplasmic catalytic domain of DesK behaves like a kinase at low temperature and like a phosphatase at high temperature. Temperature sensing involves a built-in instability caused by a group of hydrophilic residues located near the N terminus of the first transmembrane (TM) segment.