@article{HackenbergHakanpaeaeCaietal.2018,
  author    = {Hackenberg, Claudia and Hakanpaeae, Johanna and Cai, Fei and Antonyuk, Svetlana and Eigner, Caroline and Meissner, Sven and Laitaoja, Mikko and Janis, Janne and Kerfeld, Cheryl A. and Dittmann, Elke and Lamzin, Victor S.},
  title     = {Structural and functional insights into the unique CBS-CP12 fusion protein family in cyanobacteria},
  series = {Proceedings of the National Academy of Sciences of the United States of America},
  volume    = {115},
  journal   = {Proceedings of the National Academy of Sciences of the United States of America},
  number    = {27},
  publisher = {National Acad. of Sciences},
  address   = {Washington},
  issn      = {0027-8424},
  doi       = {10.1073/pnas.1806668115},
  pages     = {7141 -- 7146},
  year      = {2018},
  abstract  = {Cyanobacteria are important photosynthetic organisms inhabiting a range of dynamic environments. This phylum is distinctive among photosynthetic organisms in containing genes encoding uncharacterized cystathionine beta-synthase (CBS)-chloroplast protein (CP12) fusion proteins. These consist of two domains, each recognized as stand-alone photosynthetic regulators with different functions described in cyanobacteria (CP12) and plants (CP12 and CBSX). Here we show that CBS-CP12 fusion proteins are encoded in distinct gene neighborhoods, several unrelated to photosynthesis. Most frequently, CBS-CP12 genes are in a gene cluster with thioredoxin A (TrxA), which is prevalent in bloom-forming, marine symbiotic, and benthic mat cyanobacteria. Focusing on a CBS-CP12 from Microcystis aeruginosa PCC 7806 encoded in a gene cluster with TrxA, we reveal that the domain fusion led to the formation of a hexameric protein. We show that the CP12 domain is essential for hexamerization and contains an ordered, previously structurally uncharacterized N-terminal region. We provide evidence that CBS-CP12, while combining properties of both regulatory domains, behaves different from CP12 and plant CBSX. It does not form a ternary complex with phosphoribulokinase (PRK) and glyceraldehyde-3-phosphate dehydrogenase. Instead, CBS-CP12 decreases the activity of PRK in an AMP-dependent manner. We propose that the novel domain architecture and oligomeric state of CBS-CP12 expand its regulatory function beyond those of CP12 in cyanobacteria.},
  language  = {en}
}
@article{SchuurmansBrinkmannMakoweretal.2018,
  author    = {Schuurmans, Jasper Merijn and Brinkmann, Bregje W. and Makower, Katharina and Dittmann, Elke and Huisman, Jef and Matthijs, Hans C. P.},
  title     = {Microcystin interferes with defense against high oxidative stress in harmful cyanobacteria},
  series = {Harmful algae},
  volume    = {78},
  journal   = {Harmful algae},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {1568-9883},
  doi       = {10.1016/j.hal.2018.07.008},
  pages     = {47 -- 55},
  year      = {2018},
  abstract  = {Harmful cyanobacteria producing toxic microcystins are a major concern in water quality management. In recent years, hydrogen peroxide (H2O2) has been successfully applied to suppress cyanobacterial blooms in lakes. Physiological studies, however, indicate that microcystin protects cyanobacteria against oxidative stress, suggesting that H2O2 addition might provide a selective advantage for microcystin-producing (toxic) strains. This study compares the response of a toxic Microcystis strain, its non-toxic mutant, and a naturally non-toxic Microcystis strain to H2O2 addition representative of lake treatments. All three strains initially ceased growth upon H2O2 addition. Contrary to expectation, the non-toxic strain and non-toxic mutant rapidly degraded the added H2O2 and subsequently recovered, whereas the toxic strain did not degrade H2O2 and did not recover. Experimental catalase addition enabled recovery of the toxic strain, demonstrating that rapid H2O2 degradation is indeed essential for cyanobacterial survival. Interestingly, prior to H2O2 addition, gene expression of a thioredoxin and peroxiredoxin was much lower in the toxic strain than in its non-toxic mutant. Thioredoxin and peroxiredoxin are both involved in H2O2 degradation, and microcystin may potentially suppress their activity. These results show that microcystin-producing strains are less prepared for high levels of oxidative stress, and are therefore hit harder by H2O2 addition than non-toxic strains.},
  language  = {en}
}