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09:32
Light-mediated Reversible Modulation of the Mitogen-activated Protein Kinase Pathway during Cell Differentiation and Xenopus Embryonic Development
Published on: June 15, 2017
A non-hydrolyzable ATP derivative generates a stable complex in a light-inducible two-component system
Shivani Sharda1, Melissa S T Koay, Young-Jun Kim
1Max Planck Institute for Bioinorganic Chemistry, 45413 Mülheim, Germany.
The Journal of Biological Chemistry
|October 8, 2009
Summary
Bacterial histidine kinases (HK) and response regulators (RR) form complexes essential for signaling. This study shows HK-RR interactions require ATP and are mediated by the full phytochrome structure, not just the HK domain alone.
Area of Science:
- Biochemistry
- Molecular Biology
- Microbiology
Background:
- Bacterial two-component systems, involving histidine kinases (HK) and response regulators (RR), are crucial for cellular signal transduction.
- These systems are also found in bacterial phytochromes, regulating light-dependent processes.
- Understanding HK-RR interactions is key to deciphering these signaling pathways.
Purpose of the Study:
- To investigate the binding constants and conditions for complex formation between phytochromes CphA/CphB and their cognate response regulators RcpA/RcpB from Tolypothrix PCC7601.
- To determine the role of ATP and the phytochrome structure in mediating these interactions.
Main Methods:
- Isothermal titration calorimetry (ITC) was employed to measure binding constants.
- Recombinant histidine kinase (HK) domains and full-length phytochromes were used.
- Interactions were studied in the presence and absence of ATP and its non-hydrolyzable derivatives.
Main Results:
- Complex formation between HK and RR was observed only in the presence of ATP.
- Specific interactions were detected solely with a non-hydrolyzable ATP analog.
- The isolated HK domain did not interact with the RR, indicating the necessity of the full phytochrome structure.
- HK activity is dependent on the Pr form of the chromophore domain.
Conclusions:
- Phytochrome HK domains require the intact phytochrome structure and the Pr chromophore state for activity.
- Phosphate transfer occurs via transient protein-protein complexes, detectable by ITC with non-hydrolyzable ATP.
- These findings have implications for understanding signaling in photoreceptors with fused HK-RR domains.
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