Abstract
Phytochrom B (phyB) is a dimeric chromoprotein that detects the quantity, quality, and duration of red or far-red light throughout the entire life cycle of plants. Upon absorption of red light, phyB translocates from the cytoplasm to nucleus, and regulates gene expression through interaction with transcription factors such as basic-helix-loop-helix proteins. The PAS domain within the phyB C-terminal domain contains determinants necessary for nuclear translocation and signal transduction. Here we showed the solution structure of PAS1 domain, one of two PAS domains, determined by multidimensional NMR spectroscopy. Both the core region of a loss of function missense mutations (referred as the "Quail-box") and dimerization site were mapped on the β-sheet side, which was constituted of conserved residues among all phyAs and phyBs. Stable dimer formation of two PAS1 domains on the β-sheet side will be linked to phytochrome function.
