title: Phosphorelay of non-orthodox two component systems functions through a bi-molecular mechanism in vivo: the case of ArcB.
abstract: Two-component systems play a central part in bacterial signal transduction. Phosphorelay mechanisms have been linked to more robust and ultra-sensitive signalling dynamics. The molecular machinery that facilitates such a signalling is, however, only understood in outline. In particular the functional relevance of the dimerization of a non-orthodox or hybrid histidine kinase along which the phosphorelay takes place has been a subject of debate. We use a combination of molecular and genetic approaches, coupled to mathematical and statistical modelling, to demonstrate that the different possible intra- and inter-molecular mechanisms of phosphotransfer are formally non-identifiable in Escherichia coli expressing the ArcB non-orthodox histidine kinase used in anoxic redox control. In order to resolve this issue we further analyse the mathematical model in order to identify discriminatory experiments, which are then performed to address cis- and trans-phosphorelay mechanisms. The results suggest that exclusive cis- and trans-mechanisms will not be operating, instead the functional phosphorelay is likely to build around a sequence of allosteric interactions among the domain pairs in the histidine kinase. This is the first detailed mechanistic analysis of the molecular processes involved in non-orthodox two-component signalling and our results suggest strongly that dimerization facilitates more discriminatory proof-reading of external signals, via these allosteric reactions, prior to them being further processed.
authors: Department of Life Sciences, Imperial College London, UK. m.stumpf@imperial.ac.uk m.buck@imperial.ac.uk.
authors: Goran
authors: G
authors: Jovanovic
authors: Xia
authors: X
authors: Sheng
authors: Angelique
authors: A
authors: Ale
authors: Elisenda
authors: E
authors: Feliu
authors: Heather A
authors: HA
authors: Harrington
authors: Paul
authors: P
authors: Kirk
authors: Carsten
authors: C
authors: Wiuf
authors: Martin
authors: M
authors: Buck
authors: Michael P H
authors: MP
authors: Stumpf
mesh_terms: D004926:Escherichia coli / Q000502:physiology*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D009154:Mutation; D010766:Phosphorylation; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D011494:Protein Kinases; C065271:arcB protein, E coli