A structure-function model based on inter-domain crosstalks in phytochromes

Abstract

The molecular mechanism for the on/off switching of the phytochromes is driven by the photochromic phototransformation between the two spectrally distinct forms of the phytochromes, a red light (R, 660 nm) absorbing Pr and a far-red light (FR, 730 nm) absorbing Pfr forms.The photoactivated Pfr signals are transduced by interacting with a wide array of downstream signaling components and finally regulate genes involved in photomorphogenesis ([Quail 2002], [Wang and Deng 2003] for reviews). Our understanding as to how phytochromes perceive light signals and how the light signals are transmitted intramolecularly within the phytochrome molecules is only beginning. The photoisomerization of the chromophore modulates apoprotein:chromophore interactions, and subsequently triggers conformational changes throughout the whole phytochrome molecule via intramolecular inter-domain crosstalks ([Park et al 2000], [Kim et al 2002b]), like the well-characterized rhodopsin visual receptor in animals, as discussed in the next sections.