Light-dependent dimerisation in the N-terminal sensory module of cyanobacterial phytochrome 1

H.M. Strauss, P. Schmieder, J. Hughes

FEBS Lett.(2005) 579, 3970 - 3974

Phytochromes, photoreceptors controlling important physiological processes in plants and many prokaryotes, are photochromic biliproteins. The red-absorbing Pr ground state is converted by light into the farred-absorbing Pfr which can be photoconverted back to Pr. In plants at least Pfr is the physiologically active signalling state. Here, we show that the N-terminal photochromic module of Cph1 homodimerises reversibly and independently in Pr and Pfr, Pfr-dimers being significantly more stable. Implications for the mechanism of signal transduction are discussed.

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