Structure of a bacteriophytochrome and light-stimulated protomer swapping with a gene repressor.
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.
Institute of Integrative Biology, Biosciences Building, University of Liverpool, Crown Street, Liverpool L69 7ZB, UK.
Dom
D
Bellini
Miroslav Z
MZ
Papiz
D020816:Amino Acid Motifs; D001426:Bacterial Proteins / Q000737:chemistry*; D001664:Biliverdine / Q000737:chemistry; D001665:Binding Sites; D018360:Crystallography, X-Ray; D015964:Gene Expression Regulation, Bacterial / Q000528:radiation effects*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D010860:Pigments, Biological / Q000737:chemistry*; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D020836:Protein Structure, Quaternary; D021122:Protein Subunits / Q000737:chemistry*; D012097:Repressor Proteins / Q000737:chemistry*; D012241:Rhodopseudomonas; D015398:Signal Transduction
D001426:Bacterial Proteins; D010860:Pigments, Biological; D021122:Protein Subunits; D012097:Repressor Proteins; D001664:Biliverdine