| 研究実績の概要 |
Substrate selectivity of transporters is critical to accomplish the complex systems in biological processes. However, the molecular mechanisms of substrate selectivity of transporters have not been fully elucidated. SWEETs, which recently we identified, play essential roles through the transport activity for sucrose and/or glucose. In addition to sugars, SWEETs can transport gibberellic acid (GA), a hormone that regulates many important aspects of plant growth and development. Sugars and phytohormones are essential to the fundamental processes of plant development and growth. It has remained unclear, however, which spectrum of substrates SWEETs can transport, and how SWEETs can transport substrates as different as sucrose and GA. To understand the molecular mechanisms of substrate selectivity of plant transporters, we studied the substrate recognition of SWEETs using molecular docking and molecular dynamics. The docking studies have revealed residues of AtSWEET13 involved in binding GA and/or sucrose. To investigate the residues required to transport substrate, the in-cell transporter activity assay using fluorescent probes and mammalian cells were established. We here dissected the relative contribution of sucrose and GA by engineering the relative selectivity of SWEET13 and evaluating the ability of mutant forms to restore fertility of sweet13;14 double mutants.
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