Phosphorelay control of phycobilisome biogenesis during complementary chromatic adaptation

Abstract

For some cyanobacteria, the spectral distribution of light in the environment regulates the synthesis of specific polypeptides of the phycobilisome or light harvesting antenna complex. This process, called complementary chromatic adaptation, is controlled by a complex type of two component regulatory system. In such pathways, phosphorelay typically occurs through two histidine and two aspartate residues. Generation and complementation of mutants in CCA have uncovered three elements of this pathway, a putative sensor, RcaE, and two response regulators, RcaC and RcaF. RcaC, a large response regulator, contains two input domains, a DNA binding motif and a putative histidine phosphoacceptor domain. RcaF is a small response regulator and apparently lacks an output domain. Ordering of the pathway components has placed RcaE before RcaF, and RcaF before RcaC. This phosphorelay circuitry is novel because it has, instead of four, at least five potential phosphoacceptor domains for signal transduction.