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Our research interests lie in understanding how cells respond and adapt to changes in their environment. To address this topic, we study signal transduction in the model freshwater and soil bacterium Caulobacter crescentus. Caulobacter must respond to a variety of stressors and signals in its surroundings, such as osmotic stress, changes in pH, oxygen levels, etc. Bacteria, including Caulobacter, use protein sensory systems, called two-component signaling systems (TCSs), to sense these types of signals. These systems consist of a sensory histidine kinase that autophosphorylates and then passes the phosphoryl group to a response regulator. In response to phosphorylation, the response regulator then induces a cellular response, most often a change in gene expression (and, as a result, changes in the proteome).
Although the canonical TCS is fairly simple, many systems incorporate atypical signaling proteins and/or additional regulators. We study several such complex TCSs in Caulobacter, focusing on their regulation and physiological outputs.
Current projects in the lab:
Project 1 -The FixLJ TCS and FixT - C. crescentus employs the FixLJ TCS to sense low oxygen levels in the environment and respond accordingly for optimal respiration. This TCS also upregulates a feedback inhibitor, FixT, which inhibits the FixL histidine kinase. We previously characterized FixT in C. crescentus and found that it directly inhibits autophosphorylation activity. Work in the lab focuses on the specific protein residues and structural elements that contribute to this enzyme inhibition. In addition, we are examining other interesting features of FixT, such as an Fe-S cofactor that stabilizes FixT against degradation by the Lon protease.
Project 2 - The ChvGI and NtrYXZ TCSs - We recently began researching the interactions between two TCSs: ChvGI and NtrYX. Through this work, we identified a novel kinase regulator, NtrZ, that affects NtrX dephosphorylation by the NtrY kinase/phosphatase. The lab is now focusing on characterizing the NtrY-NtrZ interaction and interrogating the determinants and biochemical consequences of NtrX phosphorylation/dephosphorylation. In addition, we are working to understand how the ChvGI and NtrYXZ systems intertwine to regulate cellular fitness during growth in defined medium.
An overview of most of our lab space showing a variety of instruments and our lovely views of campus!
An overview of most of our lab space showing a variety of instruments and our lovely views of campus!
One of our lab workstations, as well as an incubator shaker, Vis spec, and OpenSPR instrument
One of our lab workstations, as well as an incubator shaker, Vis spec, and OpenSPR instrument
Desk/computer area along with more views of campus and a few instruments (centrifuge, gel/blot imager, and microscope)
Desk/computer area along with more views of campus and a few instruments (centrifuge, gel/blot imager, and microscope)
Our space is small but mighty!
Our space is small but mighty!
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