Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 105, Issue 33, Pages 11715-11719Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.0802149105
Keywords
flavin chromophore; phototaxis; synechocystis
Categories
Funding
- National Institutes of Health [GM40941]
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Cyanobacteria perceive and move (phototax) in response to blue light. In this study, we demonstrate that the PixD blue light-sensing using FAD (BLUF) photoreceptor that governs this response undergoes changes in oligomerization state upon illumination. Under dark conditions we observed that PixD forms a large molecular weight complex with another protein called PixE. Stoicheometric analyses, coupled with sedimentation equilibrium and size exclusion chromatography, demonstrates that PixE drives aggregation of PixD dimers into a stable PixD(10)-PixE(5) complex under dark conditions. Illumination of a flavin chromophore in PixD destabilizes the PixD(10)-PixE(5) complex into monomers of PixE and dimers of PixD. A crystallographic structure of PixD, coupled with Gibbs free energy calculation between interacting faces of PixD, lends to a model in which a light induces a conformational change in a critical PixD-interfacing loop that results in destabilization of the PixD(10)-PixE(5) complex.
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