Reversal of the histidine kinase activity by a small linker helix

Scientists have revealed new information on how red light-regulated histidine kinases function. According to the study, altering of the length of a specific ‘linker helix’ region of the protein can even reverse their enzymatic activity. The study is published in Nature Communications.

Red light regulated histidine kinases

Bacteria often sense and respond to their environment by applying receptor histidine kinase proteins. Once a histidine kinase senses an incident signal, it conveys this information to the cells by phosphorylating a response regulator protein. Bacterial phytochromes are red light sensing photoreceptors that usually function as histidine kinases. They are especially suitable model systems for studying histidine kinase signaling and for optogenetic applications.

“Optogenetics aims to control cellular events with light, and bacterial phytochromes have traits that makes them especially good for this purpose,” explains docent Heikki Takala from the University of Jyväskylä. ”Due to this reason, we have previously generated an optogenetic pREDusk tool that is based on a bacterial phytochrome.”

Reversal of  ‘pREDusk’ leads to ‘pDERusk’

An international collaboration between the groups of Dr. Heikki Takala from the University of Jyväskylä and Prof. Andreas Möglich from the University of Bayreuth have revealed key details on histidine kinase signaling. By applying modifications in their pREDusk tool, they showed how the delicate balance between kinase and phosphatase activities is fine-tuned in histidine kinase receptors. Importantly, they also revealed that certain deletions in a so-called ‘linker helix’ of the phytochrome component reverses their enzymatic activity.

The process led to development of an inverted pREDusk tool that, unlike its predecessor, can activate bacterial gene expression under red light. “We named this new tool ‘pDERusk’. This name first started as an unintended typo, but we noticed that would be a perfect name for an inverted ‘pREDusk,” Takala concludes.

Reference:

The paper ‘Leveraging the histidine kinase-phosphatase duality to sculpt two-component signaling’ can be freely accessed online at https://doi.org/10.1038/s41467-024-49251-8.