FIGURE 1.

Domain arrangements of the A. tumefaciens phytochromes and the domain swap mutants used in the present study. Agp1 has the prototypical domain arrangement of bacterial phytochromes with N-terminal PAS, GAF, and PHY domains and a C-terminal His kinase (HisK). These domains are drawn in dark gray tones. Agp2 has a similar domain arrangement, but the histidine kinase is of the HWE type, and it bears a C-terminal response regulator. Agp2 domains are drawn in light gray tones. The range of each domain is indicated above the Agp1 and Agp2 diagrams. The amino acids that are indicated by vertical bars and numbered under the Agp2 diagram refer to the point mutants that were also used in the present study. The lower four diagrams show the domain arrangements and the denomination of the domain swap mutants. Dark gray color indicates that the respective domain of Agp2 is replaced by that of Agp1.