The activity of an unusual phytochrome revealed

Scientist have revealed the biochemical activity of a model phytochrome in a new study published in Nature Communications.

Plants and bacteria constantly adapt in changes to light environment. This is achieved through photosensory proteins. Phytochromes are a group of photoreceptor proteins that respond to red light. In order to study how phytochromes function in general, scientist have concentrated on a few bacterial phytochromes. One of the most popular model phytochromes is DrBphP from Deinococcus radiodurans.

Although the structure and function of DrBphP has been studied extensively for decades, its exact role in bacteria has remained a mystery.

“We cannot conclude that the previous results with DrBphP are fully biologically relevant, unless we know that the phytochrome is a functional protein,” explains Docent Heikki Takala from the University of Jyväskylä. “Therefore, the biochemical activity of this photoreceptor would be an important link between the studies and nature.”

Light-triggered activity revealed

An international team, led by Dr. Heikki Takala and Professor Janne Ihalainen from the University of Jyväskylä, have now solved this long-standing conundrum. By using various biochemical and structural methods, they found out that the activity of DrBphP is not missing but inverted.

“Normally bacterial phytochromes function as light-gated histidine kinases, which add a phosphate moiety to their target proteins.”, describes Elina Multamäki from the University of Helsinki. “We however found out that DrBphP functions instead as a phosphatase, hence in a “reverse” direction.”

Furthermore, the team combined a phytochrome protein from two different species, where the photosensing unit was taken from D. radiodurans but the activator unit was taken from an agrobacterium (Agrobacterium fabrum), and showed that the inverted signaling mechanism could be returned back to a normal mechanism.

“These unexpected results show that the signaling of bacterial phytochromes can be more versatile than previously thought, but the photosensing function is quite universal from species to species “, concludes Professor Janne Ihalainen.

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The research was published in Nature Communications in 20th of July 2021,

For further information
Heikki Takala, Docent in Department of Biological and Environmental Science, University of Jyvaskyla, +358 46 923 6211, heikki.p.takala@jyu.fi
Janne A. Ihalainen, Professor in Department of Biological and Environmental Science, University of Jyvaskyla, +358 40 024 7979, janne.ihalainen@jyu.fi
Elina Multamäki, Graduate Student, University of Helsinki, elina.multamaki@helsinki.fi