A1 Journal article (refereed)
The interconnecting hairpin extension "arm" : An essential allosteric element of phytochrome activity (2023)

Kurttila, M., Rumfeldt, J., Takala, H., & Ihalainen, J. A. (2023). The interconnecting hairpin extension "arm" : An essential allosteric element of phytochrome activity. Structure, 31(9), 1100-1108, e1-e4. https://doi.org/10.1016/j.str.2023.06.007

JYU authors or editors

Publication details

All authors or editorsKurttila, Moona; Rumfeldt, Jessica; Takala, Heikki; Ihalainen, Janne A.

Journal or seriesStructure



Publication year2023

Publication date30/06/2023


Issue number9

Pages range1100-1108, e1-e4


Publication countryUnited Kingdom

Publication languageEnglish


Publication open accessOpenly available

Publication channel open accessPartially open access channel

Publication is parallel published (JYX)https://jyx.jyu.fi/handle/123456789/88305


In red-light sensing phytochromes, isomerization of the bilin chromophore triggers structural and dynamic changes across multiple domains, ultimately leading to control of the output module (OPM) activity. In between, a hairpin structure, "arm", extends from an interconnecting domain to the chromophore region. Here, by removing this protein segment in a bacteriophytochrome from Deinococcus radiodurans (DrBphP), we show that the arm is crucial for signal transduction. Crystallographic, spectroscopic, and biochemical data indicate that this variant maintains the properties of DrBphP in the resting state. Spectroscopic data also reveal that the armless systems maintain the ability to respond to light. However, there is no subsequent regulation of OPM activity without the arms. Thermal denaturation reveals that the arms stabilize the DrBphP structure. Our results underline the importance of the structurally flexible interconnecting hairpin extensions and describe their central role in the allosteric coupling of phytochromes.

Keywordsproteinsreceptors (biochemistry)cell signalingphotochemistry

Free keywordsphytochrome; photosensor; signal transduction; thermal stability; allostery; PACS; 87.15; 87.14 2000 MSC; 92-05; 92-11; histidine kinanase; photoreceptor; structure and function; protein structure

Contributing organizations

Related projects

Ministry reportingYes

Reporting Year2023

JUFO rating2

Last updated on 2024-15-06 at 01:06