Allostery in bacterial transcription factors arises from changes in global low-frequency protein dynamics. Amino acids that regulate low-frequency dynamics are identified and seen to be evolutionarily conserved.

Plant nucleotide-binding leucine–rich repeat (NLR) proteins enable the immune system to recognize and respond to pathogen attack. An early consequence of immune activation is transcriptional reprogramming, and some NLRs have been shown to act in the nucleus and interact with transcription factors. The Rx1 NLR protein of potato is further able to bind and distort double-stranded DNA. However, Rx1 host targets that support a role for Rx1 in transcriptional reprogramming at DNA are unknown. Here, we report a functional interaction between Rx1 and NbGlk1, a Golden2-like transcription factor. Rx1 binds to NbGlk1 in vitro and in planta. NbGlk1 binds to known Golden2-like consensus DNA sequences. Rx1 reduces the binding affinity of NbGlk1 for DNA in vitro. NbGlk1 activates cellular responses to potato virus X, whereas Rx1 associates with NbGlk1 and prevents its assembly on DNA in planta unless activated by PVX. This study provides new mechanistic insight into how an NLR can coordinate an immune signaling response at DNA following pathogen perceptions.

Carbon dioxide is fundamental to the physiology of all organisms. There is considerable interest in the precise molecular mechanisms that organisms use to directly sense CO 2 . Here we demonstrate that a mammalian recombinant G-protein-activated adenylyl cyclase and the related Rv1625c adenylyl cyclase of Mycobacterium tuberculosis are specifically stimulated by CO 2 . Stimulation occurred at physiological concentrations of CO 2 through increased k cat . CO 2 increased the affinity of enzyme for metal co-factor, but contact with metal was not necessary as CO 2 interacted directly with apoenzyme. CO 2 stimulated the activity of both G-protein-regulated adenylyl cyclases and Rv1625c in vivo. Activation of G-protein regulated adenylyl cyclases by CO 2 gave a corresponding increase in cAMP-response element-binding protein (CREB) phosphorylation. Comparison of the responses of the G-protein regulated adenylyl cyclases and the molecularly, and biochemically distinct mammalian soluble adenylyl cyclase revealed that whereas G-protein-regulated enzymes are responsive to CO 2 , the soluble adenylyl cyclase is responsive to both CO 2 and bicarbonate ion. We have, thus, identified a signaling enzyme by which eukaryotes can directly detect and respond to fluctuating CO 2 .

Background: Direct targets for plant NLR proteins in immune signaling are largely unknown.Results: The Rx1 NLR protein of potato binds and distorts DNA following pathogen perception, resulting in immune activation.Conclusion: DNA is a direct signaling target for a plant NLR immune receptor.Significance: Plant NLR receptors might regulate immune transcriptional responses by directly interacting with plant chromatin.

Background: Protein allostery can be communicated purely through altered entropy.Results: Altered cAMP binding strength in CAP results in changes to entropy-driven allostery.Conclusion: The requirement to maintain allostery constrains evolution of the ligand-binding site in CAP.Significance: Entropy-driven processes can constrain amino acid covariation in evolution.