Sequential conformational transitions and α-helical supercoiling regulate a sensor histidine kinase.

Area of Science:

• Bacterial and plant signaling pathways.
• Molecular mechanisms of signal transduction.
• Protein structural dynamics.

Background:

• Sensor histidine kinases (SHK) are crucial for cellular sensing in bacteria and plants.
• SHK typically comprise sensor, linker, and kinase modules, with known structures for many components.
• The precise structural regulation of the kinase module remains poorly understood.

Purpose of the Study:

• To elucidate the structural mechanism of kinase domain activation in sensor histidine kinases.
• To visualize dynamic structural changes in response to light activation.
• To provide a structural template for signal transduction in SHK.

Main Methods:

• Utilized nano- to millisecond time-resolved X-ray scattering.
• Investigated the light-sensitive model histidine kinase YF1.
• Observed structural changes upon blue light activation.

Main Results:

• The coiled coil linker and associated histidine kinase domains exhibit a left-handed rotation within microseconds.
• A subsequent, slower step involves internal rearrangement of the kinase domains.
• These dynamics reveal a two-step activation mechanism.

Conclusions:

• The study presents a novel structural mechanism for sensor histidine kinase activation.
• This mechanism involves distinct rotational and rearrangement steps.
• The findings offer a template for understanding signal transduction in SHK.