Phototropin-1 (PHOT1) Arabidopsis Thaliana Recombinant Protein

Blue-light photoreceptor. Contains a light activated serine-threonine kinase domain and LOV1 and LOV2 repeats. Mutants are defective in blue-light response. Mediates blue light-induced growth enhancements. PHOT1 and PHOT2 mediate blue light-dependent activation of the plasma membrane H+-ATPase in guard cell protoplasts. PHOT1 undergoes blue-light-dependent autophosphorylation. At least eight phosphorylation sites have been identified in PHOT1. Phosphorylation of serine851 in the activation loop of PHOT1 appears to be required for stomatal opening, chloroplast accumulation, leaf flattening, and phototropism, and phosphorylation of serine849 may also contribute to the regulation of these responses. Phosphorylation-dependent binding of 14-3-3 proteins to the Hinge1 region of PHOT1 appears to require serine350 and serine376.

Protein kinase that acts as a blue light photoreceptor in a signal-transduction pathway for photo-induced movements. Phosphorylates BLUS1, a kinase involved in stomatal opening. Required for blue light mediated mRNA destabilization. Mediates calcium spiking of extracellular origin in response to a low rate of blue light. Also mediates rapid membrane depolarization and growth inhibition in response to blue light. Necessary for root phototropism. Involved in hypocotyl phototropism under a low rate but not under a high rate of blue light. Contributes to the chloroplast accumulation but seems not to be required for chloroplast translocation. Regulates stomata opening and photomorphogenesis response of leaf tissue. Confers sensitivity to drought. Not involved in hypocotyl elongation inhibition, anthocyanin accumulation or cotyledon opening.