4GW9

Structure of a bacteriophytochrome and light-stimulated protomer swapping with a gene repressor.

(2012) Structure 20: 1436-1446

• PubMed: 22795083 Search on PubMed
• DOI: https://doi.org/10.1016/j.str.2012.06.002
• Primary Citation of Related Structures:  
  4GW9


• PubMed Abstract: 
  

  Phytochromes are photoreceptors in phototropic organisms that respond to light conditions by changing interactions between a response regulator and DNA. Bacterial phytochromes (BphPs) comprise an input photosensory core domain (PCD) and an output transducing domain (OTD). We report the structure of a BphP containing both PCD and the majority of its OTD, and demonstrate interaction with its cognate repressor. The OTD of RpBphP1, from Rhodopseudomonas palustris, is composed of a PAS/PAC domain and, to our knowledge, a hitherto unrecognized two-helix output sensor (HOS) domain. Unlike canonical BphPs, it does not transmit phosphorelay signals but forms a complex with the transcriptional repressor RpPpsR2 on photoconversion with far-red light. We show that HOS is essential for complex formation and that the anti-parallel dimer geometry is crucial in achieving HOS domain activation and protomer swapping under the control of light. These results provide insights into the steps taken by a two-component signaling system.

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Organizational Affiliation: 

Institute of Integrative Biology, Biosciences Building, University of Liverpool, Crown Street, Liverpool L69 7ZB, UK.