Tertiary and quaternary structures of phytochrome A

Phytochrome A (phy A) is a major member of phytochrome family and is photoconvertible between a red light (Pr) and a far-red light absorbing (Pfr) form. The Pfr form predominantly regulates downstream signaling cascades leading to a variety of photomorphogenic responses ([Smith 2000], [Fankhauser 2001], [Quail 2002]). In the last decade, molecular biological studies have identified functionally important residues and sequence motifs in phyA ([Park et al 2000]). However, the molecular structure of phy A and structural changes upon Pr-Pfr phototransformation are still unclear. Here, we describe our recent results on phyA structures with a brief review of structural studies on phytochromes.