Dimerization of the plant photoreceptor phototropin is probably mediated by the LOV1 domain |
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Authors: | Salomon Michael Lempert Ulrika Rüdiger Wolfhart |
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Institution: | Department Biologie I (Botanik), Ludwig-Maximilians-Universit?t München, Menzingerstr. 67, 80638 München, Germany. |
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Abstract: | Phototropin is a membrane-bound UV-A/blue light photoreceptor of plants responsible for phototropism, chloroplast migration and stomatal opening. Characteristic are two LOV domains, each binding one flavin mononucleotide, in the N-terminal half and having a serine/threonine kinase domain in the C-terminal half of the molecule. We purified the N-terminal half of oat phototropin 1, containing LOV1 and LOV2 domains, as a soluble fusion protein with the calmodulin binding peptide (CBP) by expression in Escherichia coli. Gel chromatography showed that it was dimeric in solution. While the fusion protein CBP-LOV2 was exclusively monomeric in solution, the fusion protein CBP-LOV1 occurred as monomer and dimer. The proportion of dimer increased on prolonged incubation. We conclude that native phototropin is a dimer and that the LOV1 domain is probably responsible for dimerization. |
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