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Start Over Author "Tiyu Gao" Journal proceedings of the national academy of sciences of the united states of america
3 results on '"Tiyu Gao"'

1. The KaiA protein of the cyanobacterial circadian oscillator is modulated by a redox-active cofactor

Author

Yong-Gang Chang, Jennifer Bridwell-Rabb, Thammajun L. Wood, David P. Barondeau, Tiyu Gao, Susan S. Golden, Yong Ick Kim, and Andy LiWang

Subjects
Models, Molecular, Circadian clock, Bacterial Proteins, KaiC, KaiA, Circadian rhythm, Binding site, Phosphorylation, Nuclear Magnetic Resonance, Biomolecular, Synechococcus, Multidisciplinary, Binding Sites, biology, Circadian Rhythm Signaling Peptides and Proteins, Protein Stability, Biological Sciences, biology.organism_classification, Recombinant Proteins, Cell biology, Circadian Rhythm, Protein Structure, Tertiary, Dibromothymoquinone, Signal transduction, Protein Multimerization, Oxidation-Reduction, Protein Kinases, Signal Transduction
Abstract

The circadian rhythms exhibited in the cyanobacterium Synechococcus elongatus are generated by an oscillator comprised of the proteins KaiA, KaiB, and KaiC. An external signal that commonly affects the circadian clock is light. Previously, we reported that the bacteriophytochrome-like protein CikA passes environmental signals to the oscillator by directly binding a quinone and using cellular redox state as a measure of light in this photosynthetic organism. Here, we report that KaiA also binds the quinone analog 2,5-dibromo-3-methyl-6-isopropyl- p -benzoquinone (DBMIB), and the oxidized form of DBMIB, but not its reduced form, decreases the stability of KaiA in vivo, causes multimerization in vitro, and blocks KaiA stimulation of KaiC phosphorylation, which is central to circadian oscillation. Our data suggest that KaiA directly senses environmental signals as changes in redox state and modulates the circadian clock.

Published
2010

2. Quinone sensing by the circadian input kinase of the cyanobacterial circadian clock

Author

Tiyu Gao, Susan S. Golden, Andy LiWang, and Natalia B. Ivleva

Subjects
Magnetic Resonance Spectroscopy, Light, Circadian clock, Plastoquinone, Biology, Cyanobacteria, Sensitivity and Specificity, chemistry.chemical_compound, Bacterial Proteins, KaiC, KaiA, Circadian rhythm, Phosphorylation, Chronobiology, Multidisciplinary, Circadian Rhythm Signaling Peptides and Proteins, Cell Membrane, Gene Expression Regulation, Bacterial, Biological Sciences, Bacterial circadian rhythms, Cell biology, Circadian Rhythm, Molecular Weight, Light intensity, Dibromothymoquinone, chemistry, Biochemistry, Oxidation-Reduction, Protein Kinases, Protein Binding
Abstract

Circadian rhythms are endogenous cellular programs that time metabolic and behavioral events to occur at optimal times in the daily cycle. Light and dark cycles synchronize the endogenous clock with the external environment through a process called entrainment. Previously, we identified the bacteriophytochrome-like circadian input kinase CikA as a key factor for entraining the clock in the cyanobacterium Synechococcus elongatus PCC 7942. Here, we present evidence that CikA senses not light but rather the redox state of the plastoquinone pool, which, in photosynthetic organisms, varies as a function of the light environment. Furthermore, CikA associates with the Kai proteins of the circadian oscillator, and it influences the phosphorylation state of KaiC during resetting of circadian phase by a dark pulse. The abundance of CikA varies inversely with light intensity, and its stability decreases in the presence of the quinone analog 2,5-dibromo-3-methyl-6-isopropyl- p -benzoquinone (DBMIB). The pseudo-receiver domain of CikA is crucial for sensitivity to DBMIB, and it binds the quinone directly, a demonstration of a previously unrecognized ligand-binding role for the receiver fold. Our results suggest that resetting the clock in S. elongatus is metabolism-dependent and that it is accomplished through the interaction of the circadian oscillator with CikA.

Published
2006

3. Quinone sensing by the circadian input kinase of the cyanobacterial circadian clock.

Author

Ivleva, Natalia B., Tiyu Gao, LiWang, Andy C., and Golden, Susan S.

Subjects
*QUINONE, *PLANT pigments, *BIOLOGICAL rhythms, *CYANOBACTERIA, *ELECTRON transport, *CELL metabolism
Abstract

Circadian rhythms are endogenous cellular programs that time metabolic and behavioral events to occur at optimal times in the daily cycle. Light and dark cycles synchronize the endogenous clock with the external environment through a process called entrainment. Previously, we identified the bacteriophytochrome-like circadian input kinase CikA as a key factor for entraining the clock in the cyanobacterium Synechococcus elongatus PCC 7942. Here, we present evidence that CikA senses not light but rather the redox state of the plastoquinone pool, which, in photosynthetic organisms, varies as a function of the light environment. Furthermore, CikA associates with the Kai proteins of the circadian oscillator, and it influences the phosphorylation state of KaiC during resetting of circadian phase by a dark pulse. The abundance of CikA varies inversely with light intensity, and its stability decreases in the presence of the quinone analog 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone (DBMIB). The pseudo-receiver domain of CikA is crucial for sensitivity to DBMIB, and it binds the quinone directly, a demonstration of a previously unrecognized ligand-binding role for the receiver fold. Our results suggest that resetting the clock in S. elongatus is metabolism-dependent and that it is accomplished through the interaction of the circadian oscillator with CikA. [ABSTRACT FROM AUTHOR]

Published
2006
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