Phototropins are plant proteins that respond to blue light and regulate processes such as phototropism and leaf opening. On exposure to light, a per-ARNT-Sim (PAS) domain forms a covalent bond with a flavin chromophore, and this process somehow activates a kinase domain. Harper et al. used nuclear magnetic resonance spectroscopy to show that an α-helix located outside of the PAS domain core associates with the domain in the dark, but the interaction is disrupted in the illuminated state. This conformational change likely couples light-dependent bond formation to kinase activation.
S. M. Harper, L. C. Neil, K. H. Gardner, Structural basis of a phototropin light switch. Science 301, 1541-1544 (2003). [Abstract] [Full Text]
