Abstract
Two-component signal transduction systems mediate adaptation to environmental changes in bacteria, plants, fungi, and protists. Each two-component system consists of a sensor histidine kinase and a response regulator. Chloroplast sensor kinase (CSK) is a modified sensor histidine kinase found in chloroplasts—photosynthetic organelles of plants and algae. CSK regulates the transcription of chloroplast genes in response to changes in photosynthetic electron transport. In this study, the full-length and truncated forms of Arabidopsis CSK proteins were overexpressed and purified in order to characterise their kinase and redox sensing activities. Our results show that CSK contains a modified kinase catalytic domain that binds ATP with high affinity and forms a quinone adduct that may confer redox sensing activity.
Highlights
Photosynthesis converts light energy from the sun into useful chemical energy
Each two-component system consists of a sensor histidine kinase and a response regulator
Chloroplast sensor kinase (CSK) is a modified sensor histidine kinase found in chloroplasts—photosynthetic organelles of plants and algae
Summary
Photosynthesis converts light energy from the sun into useful chemical energy. This important biological process takes place in some prokaryotes and in chloroplasts— bioenergetic organelles of eukaryotic plants and algae. The redox state of the PQ pool controls transcription of chloroplast DNA, regulating expression of genes that encode reaction-centre proteins of PS II and PS I, initiating a long-term light quality acclimatory process known as photosystem stoichiometry adjustment (Pfannschmidt et al 1999). Prokaryotes from which chloroplasts originated, a similar redox control of photosystem stoichiometry is observed (Fujita 1997; Murakami et al 1997)
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