2017/12/27
RIKEN
Keio University
A joint research team, including Visiting Researcher Koji Okajima (Project Assistant Professor at the Graduate School of Science and Technology, Keio University) and Unit Leader Masaki Yamamoto of the Biomolecular Characterization Unit, RIKEN SPring-8 Center, has revealed the full-length three-dimensional structure of phototropin 2, a blue-light receptor protein that controls phototropism and chloroplast intracellular movement in plants, using small-angle X-ray scattering with synchrotron radiation at the large synchrotron radiation facility SPring-8.
In 1880, Charles Darwin and his colleagues discovered "phototropism," the movement in which plant stems and other parts bend toward light to optimize photosynthetic efficiency. Subsequent research has identified phototropin 1 and phototropin 2 as the proteins responsible for phototropism, which are regulated by blue light reception. In particular, when phototropin 2 receives blue light, the signal is transmitted to its kinase domain, which then phosphorylates other proteins to induce various cellular movements. However, the mechanism for converting the physical stimulus of blue light into the biological signal of phosphorylation has not been elucidated, and it remains a major challenge in this field.
The joint research team has now succeeded in the large-scale expression and biochemical preparation of full-length phototropin 2, which had previously been difficult, and investigated its three-dimensional structure using synchrotron radiation at SPring-8. The results revealed that the molecule undergoes a significant conformational change upon blue light reception and clarified the roles of the two light-receiving domains that constitute phototropin 2, LOV1 and LOV2.
This achievement is expected to lead to a better understanding of photosensing in living organisms. Furthermore, photoreceptor molecules like phototropin are beginning to be used in optogenetics, a field that uses light to control cells. If the molecular mechanism for converting light stimuli into phosphorylation can be elucidated, applications in optogenetics for controlling gene expression with light can also be expected.
This research was published in the online edition (dated December 1) of the American scientific journal "Journal of Biological Chemistry" prior to its print publication.
*Joint Research Team
RIKEN SPring-8 Center, Research and Development Division for Synchrotron Radiation Utilization
Beamline Infrastructure Research Department, Biomolecular Characterization Unit
Trainee: Mao Oide
(First-year Doctoral Programs student, Graduate School of Science and Technology, Keio University)
Visiting Researcher: Koji Okajima
(Project Assistant Professor, Graduate School of Science and Technology, Keio University)
Trainee (at the time of research): Yuki Sekiguchi
Visiting Researcher: Tomotaka Oroguchi
(Senior Assistant Professor, Faculty of Science and Technology, Keio University)
Researcher: Takaaki Hikima
Unit Leader: Masaki Yamamoto
Visiting Chief Scientist: Masayoshi Nakasako
(Professor, Faculty of Science and Technology, Keio University)
RIKEN Center for Sustainable Resource Science, Plant Immunity Research Group
Visiting Researcher: Hirofumi Nakagami
Graduate School of Frontier Biosciences, Osaka University
Project Associate Professor: Takayuki Kato
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