Espinosa J.,University of Alicante |
Lopez-Redondo M.-L.,Institute Biomedicina Of Valencia Csic And Ciberer |
Miguel-Romero L.,Institute Biomedicina Of Valencia Csic And Ciberer |
Neira J.L.,University Miguel Hernández |
And 3 more authors.
Biochimica et Biophysica Acta - Gene Regulatory Mechanisms | Year: 2012
Cyanobacteria respond to environmental stress conditions by adjusting their photosynthesis machinery. In Synechococcus sp. PCC 7942, phycobilisome degradation and other acclimation responses after nutrient or high light stress require activation by the phosphorylation-independent response regulator NblR. Structural modelling of its receiver domain suggested a role for Cys69 and Cys96 on activation of NblR. Here, we investigate this hypothesis by engineering Cys to Ala substitutions. In vivo and in vitro analyses indicated that mutations Cys69Ala and/or Cys96Ala have a minor impact on NblR function, structure, size, or oligomerization state of the protein, and that Cys69 and Cys96 do not seem to form disulphide bridges. Our results argue against the predicted involvement of Cys69 and Cys96 on NblR activation by redox sensing. © 2012 Elsevier B.V..
PubMed | Institute Biomedicina Of Valencia Csic And Ciberer
Type: Journal Article | Journal: FEBS letters | Year: 2010
The small regulator SipA, interacts with the ATP-binding domain of non-bleaching sensor histidine kinase (NblS), the most conserved histidine kinase in cyanobacteria. NblS regulates photosynthesis and acclimation to a variety of environmental conditions. We show here that SipA is a highly stable protein in a wide pH range, with a thermal denaturation midpoint of 345 K. Circular dichroism and 1D 1H NMR spectroscopies, as well as modelling, suggest that SipA is a beta-II class protein, with short strands followed by turns and long random-coil polypeptide patches, matching the SH3 fold. The experimentally determined m-value and the heat capacity change upon thermal unfolding (DeltaCp) closely agreed with the corresponding theoretical values predicted from the structural model, further supporting its accuracy.
Lopez-Redondo M.L.,Institute Biomedicina Of Valencia Csic And Ciberer |
Moronta F.,University of Alicante |
Salinas P.,University of Alicante |
Espinosa J.,University of Alicante |
And 4 more authors.
Molecular Microbiology | Year: 2010
NblS, the most conserved histidine kinase in cyanobacteria, regulates photosynthesis and acclimatization to a variety of environmental conditions. We used in silico, in vivo and in vitro approaches to identify RpaB and SrrA as the cognate response regulators of NblS and to characterize relevant interactions between components of this signalling system. While genetic analysis showed the importance of the NblS to RpaB phosphorylation branch for culture viability in Synechococcus elongatus PCC 7942, in vitro assays indicated a strong preference for NblS to phosphorylate SrrA. This apparent discrepancy can be explained by environmental insulation of the RpaB pathway, achieved by RpaB-dependent repression of srrA under standard, low light culture conditions. After a strong but transient increase in srrA expression upon high light exposure, negative regulation of srrA and other high light inducible genes takes place, suggesting cooperation between pathways under environmental conditions in which both RpaB and SrrA are present. Complex regulatory interactions between RpaB and SrrA, two response regulators with a common evolutionary origin that are controlled by a single histidine kinase, are thus emerging. Our results provide a paradigm for regulatory interactions between response regulators in a branched two-component system. © 2010 Blackwell Publishing Ltd.