Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: May 26, 2005
Publication Date: N/A
A retrospective view of our studies on D1 protein over the years is presented in this book chapter. The D1 protein is a rapidly turning over thylakoid-integral, essential component of the photosystem II reaction center and critical to photosynthetic electron transport. Over three decades, considerable structural and functional information was amassed concerning the life cycle of the D1 protein and the region of the molecule where primary light-dependent cleavage occurred. Two major steps were uncovered regarding radiance-driven D1 degradation. First, depending on incident radiation, one or more photoreceptors, characterized by specific action spectra, are activated. Then, the energized photoreceptor, directly or indirectly, activates a cleavage site resulting in the appearance of a specific breakdown product. While these findings provided some detail concerning mechanism, they skirted the issue of dual functionality of the D1 protein: a central scaffolding protein of the PS II reaction center core that inexplicably turns over more rapidly than other core and PS II proteins. We suggest that a signal whose amplitude varies with the rate of D1 protein turnover acts as the plant's light meter, setting in motion a process that helps the plant to adjust to changing light conditions.