Browsing by Author "Rockwell, Nathan C."

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Cyanobacteriochrome-based photoswitchable adenylyl cyclases (cPACs) for broad spectrum light regulation of cAMP levels in cells
(2018-06) Blain-Hartung, Matthew; Rockwell, Nathan C.; Moreno, Marcus V.; Martin, Shelley S.; Gan, Fei; Bryant, Donald A.; Lagarias, J. Clark
Class III adenylyl cyclases generate the ubiquitous second messenger cAMP from ATP often in response to environmental or cellular cues. During evolution, soluble adenylyl cyclase catalytic domains have been repeatedly juxtaposed with signal-input domains to place cAMP synthesis under the control of a wide variety of these environmental and endogenous signals. Adenylyl cyclases with light-sensing domains have proliferated in photosynthetic species depending on light as an energy source, yet are also widespread in nonphotosynthetic species. Among such naturally occurring light sensors, several flavin-based photoactivated adenylyl cyclases (PACs) have been adopted as optogenetic tools to manipulate cellular processes with blue light. In this report, we report the discovery of a cyanobacteriochrome-based photoswitchable adenylyl cyclase (cPAC) from the cyanobacterium Microcoleus sp. PCC 7113. Unlike flavin-dependent PACs, which must thermally decay to be deactivated, cPAC exhibits a bistable photocycle whose adenylyl cyclase could be reversibly activated and inactivated by blue and green light, respectively. Through domain exchange experiments, we also document the ability to extend the wavelength-sensing specificity of cPAC into the near IR. In summary, our work has uncovered a cyanobacteriochrome-based adenylyl cyclase that holds great potential for the design of bistable photoswitchable adenylyl cyclases to fine-tune cAMP-regulated processes in cells, tissues, and whole organisms with light across the visible spectrum and into the near IR.
Extensive remodeling of a cyanobacterial photosynthetic apparatus in far-red light
(American Association for the Advancement of Science, 2014-08) Gan, Fei; Zhang, Shuyi; Rockwell, Nathan C.; Martin, Shelley; Langarias, J. Clark; Bryant, Donald A.; Gan, Fei; Zhang, Shuyi; Rockwell, Nathan C.; Martin, Shelley; Langarias, J. Clark; Bryant, Donald A.
Cyanobacteria are unique among bacteria in performing oxygenic photosynthesis, often together with nitrogen fixation and, thus, are major primary producers in many ecosystems. The cyanobacterium, Leptolyngbya sp. strain JSC-1, exhibits an extensive photoacclimative response to growth in far-red light that includes the synthesis of chlorophylls d and f. During far-red acclimation, transcript levels increase ≥2-fold for ~900 genes and decrease ≥2-fold for ~2000 genes. Core subunits of photosystem I, photosystem II, and phycobilisomes are replaced by proteins encoded in a 21-gene cluster that includes a knotless red/far-red phytochrome and two response regulators. This acclimative response enhances light harvesting for wavelengths complementary to the growth light (λ = 700 to 750 nm) and enhances oxygen evolution in far-red light.
Genomic analysis reveals key aspects of prokaryotic symbiosis in the phototrophic consortium “Chlorochromatium aggregatum.”
(2013-11) Liu, Zhenhua; Müller, J.; Li, T.; Alvey, R. M.; Vogl, K.; Frigaard, N. U.; Rockwell, Nathan C.; Tomsho, Lynn P.; Schuster, Stephan C.; Henke, P.; Rohde, M.; Overmann, J.; Bryant, Donald A.
Background: ‘Chlorochromatium aggregatum’ is a phototrophic consortium, a symbiosis that may represent the highest degree of mutual interdependence between two unrelated bacteria not associated with a eukaryotic host. ‘Chlorochromatium aggregatum’ is a motile, barrel-shaped aggregate formed from a single cell of ‘Candidatus Symbiobacter mobilis”, a polarly flagellated, non-pigmented, heterotrophic bacterium, which is surrounded by approximately 15 epibiont cells of Chlorobium chlorochromatii, a non-motile photolithoautotrophic green sulfur bacterium. Results: We analyzed the complete genome sequences of both organisms to understand the basis for this symbiosis. Chl. chlorochromatii has acquired relatively few symbiosis-specific genes; most acquired genes are predicted to modify the cell wall or function in cell-cell adhesion. In striking contrast, ‘Ca. S. mobilis’ appears to have undergone massive gene loss, is probably no longer capable of independent growth, and thus may only reproduce when consortia divide. A detailed model for the energetic and metabolic bases of the dependency of ‘Ca. S. mobilis’ on Chl. chlorochromatii is described. Conclusions: Genomic analyses suggest that three types of interactions lead to a highly sophisticated relationship between these two organisms. Firstly, extensive metabolic exchange, involving carbon, nitrogen, and sulfur sources as well as vitamins, occurs from the epibiont to the central bacterium. Secondly, ‘Ca. S. mobilis’ can sense and move towards light and sulfide, resources that only directly benefit the epibiont. Thirdly, electron cycling mechanisms, particularly those mediated by quinones and potentially involving shared protonmotive force, could provide an important basis for energy exchange in this and other symbiotic relationships.
Tables S1 and S2 [dataset]
(2014-08) Gan, Fei; Zhang, Shuyi; Rockwell, Nathan C.; Martin, Shelley; Langarias, J. Clark; Bryant, Donald A.
This dataset is associated with the following article: Gan, F., S. Zhang, N. C. Rockwell, S. S. Martin, J. C. Lagarias, and D. A. Bryant. “Extensive Remodeling of a Cyanobacterial Photosynthetic Apparatus in Far-Red Light." Science 345, no. 6202 (August 21, 2014): 1312-1317. doi:10.1126/science.1256963