Abstract
The molecular structures of pea large phytochrome A lacking 6-kDa N-terminal polypeptide were studied by small-angle X-ray scattering for both the Pr and Pfr forms. A new sample preparation protocols yielded well monodispersive solutions of Pr and enabled to reveal the dimeric association, to determine the molecular dimensions and to simulate the molecular structure including the assignment of functional regions. The monodispersiveness was preserved under red-light irradiation. The significant differences in scattering profiles between Pr and Pfr were explained as a rearrangement of the functional regions in the photoconversion. Red-light induced structural changes in Pfr were fully reversible mostly due to thermal relaxation processes.
