Protein Dynamics in Phosphoryl-Transfer Signaling Mediated by Two-Component Systems

International audienceThe ability to perceive the environment, an essential attribute in living organisms, is linked to the evolution of signaling proteins that recognize specific signals and execute predetermined responses. Such proteins constitute concerted systems that can be as simple as a unique protein, able to recognize a ligand and exert a phenotypic change, or extremely complex pathways engaging dozens of different proteins which act in coordination with feedback loops and signal modulation. To understand how cells sense their surroundings and mount specific adaptive responses, we need to decipher the molecular workings of signal recognition, internalization, transfer, and conversion into chemical changes inside the cell. Protein allostery and dynamics play a central role. Here, we review recent progress on the study of two-component systems, important signaling machineries of prokaryotes and lower eukaryotes. Such systems implicate a sensory histidine kinase and a separate response regulator protein. Both components exploit protein flexibility to effect specific conformational rearrangements, modulating protein-protein interactions, and ultimately transmitting information accurately. Recent work has revealed how histidine kinases switch between discrete functional states according to the presence or absence of the signal, shifting key amino acid positions that define their catalytic activity. In concert with the cognate response regulator's allosteric changes, the phosphoryl-transfer flow during the signaling process is exquisitely fine-tuned for proper specificity, efficiency and directionality

The legacy of Carl Woese and Wolfram Zillig: from phylogeny to landmark discoveries.

International audienceTwo pioneers of twentieth century biology passed away during the past decade, Wolfram Zillig in April 2005 and Carl Woese in December 2012. Among several other accomplishments, Woese has been celebrated for the discovery of the domain Archaea and for establishing rRNA as the 'Rosetta Stone' of evolutionary and environmental microbiology. His work inspired many scientists in various fields of biology, and among them was Wolfram Zillig, who is credited with the discovery of several unique molecular features of archaea. In this Essay, we highlight the remarkable achievements of Woese and Zillig and consider how they have shaped the archaeal research landscape