Abstract
Phototropins (phot1 and phot2) are membrane-bound blue light photoreceptors that function in phototropism, chloroplast relocation, stomatal opening, and leaf flattening in Arabidopsis. The molecular structure of phototropin is well conserved for the distinct biochemical roles; two LOV domains in its N-terminal half as a photosensory domain and a Ser/Thr kinase domain in its C-terminal half as a signal transducer. Here, we studied the structural roles of the N-terminus of phot2 (P2N) in vivo and in vitro. Size exclusion chromatography suggested that phot2 might exist as a multimer form around 500 kDa in vivo. In addition, the recombinant P2N and P2NN (the N-terminus of P2N including LOV1), but not P2NC (the C-terminus of P2N including LOV2) were detected as a tetramer, respectively, suggesting that the region of LOV1 domain was responsible for the multimeric formation of phot2. Physiological roles of the P2N will be also discussed.
