Funding Organization(s): National Science Foundation (NSF, United States), National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
Primary Citation of Related Structures: 5BRJ, 5IC5
PubMed Abstract:
Bacteriophytochrome photoreceptors (BphPs) and their cognate response regulators make up two-component signal transduction systems which direct bacteria to mount phenotypic responses to changes in environmental light quality. Most of these systems utilize single-domain response regulators to transduce signals through unknown pathways and mechanisms ...
Bacteriophytochrome photoreceptors (BphPs) and their cognate response regulators make up two-component signal transduction systems which direct bacteria to mount phenotypic responses to changes in environmental light quality. Most of these systems utilize single-domain response regulators to transduce signals through unknown pathways and mechanisms. Here we describe the photocycle and autophosphorylation kinetics of RtBphP1, a red light-regulated histidine kinase from the desert bacterium Ramlibacter tataouinensis RtBphP1 undergoes red to far-red photoconversion with rapid thermal reversion to the dark state. RtBphP1 is autophosphorylated in the dark; this activity is inhibited under red light. The RtBphP1 cognate response regulator, the R. tataouinensis bacteriophytochrome response regulator (RtBRR), and a homolog, AtBRR from Agrobacterium tumefaciens, crystallize unexpectedly as arm-in-arm dimers, reliant on a conserved hydrophobic motif, hFWAhL (where h is a hydrophobic M, V, L, or I residue). RtBRR and AtBRR dimerize distinctly from four structurally characterized phytochrome response regulators found in photosynthetic organisms and from all other receiver domain homodimers in the Protein Data Bank. A unique cacodylate-zinc-histidine tag metal organic framework yielded single-wavelength anomalous diffraction phases and may be of general interest. Examination of the effect of the BRR stoichiometry on signal transduction showed that phosphorylated RtBRR is accumulated more efficiently than the engineered monomeric RtBRR (RtBRRmon) in phosphotransfer reactions. Thus, we conclude that arm-in-arm dimers are a relevant signaling intermediate in this class of two-component regulatory systems.
Organizational Affiliation:
Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin, USA forest@bact.wisc.edu.
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