Molecule of the Month: Two-component Systems
Bacteria respond to their environment with two-component sensing systems.
Signaling with Two Components
Variations on a Theme
Exploring the Structure
Histidine Kinase and Response Regulator (PDB entry 3dge)
PDB entry 3dge captures the passing of the signal from the sensory protein to the response regulator. Two copies of the response regulator (green) are bound to the sensory protein (blue), placing the key aspartate on the regulator close to the key histidine on the sensory protein (both shown with atomic spheres). The structure also includes a sulfate ion (yellow) in the approximate position occupied by the phosphate that is normally transferred. To explore this structure in more detail, click on the image for an interactive JSmol.
Topics for Further Discussion
- The sensory protein is very dynamic, flexing when it senses its appropriate target and allowing the kinase domain to phosphorylate the histidine. PDB entry 4biv captures this process: chain A has the kinase in an inactive conformation, and chain B has the kinase domain next to His248, ready to phosphorylate it.
- Because two-component system proteins are modular, scientists often break them into pieces when they determine atomic structures of them. You can use the Protein Feature View to see how these pieces fit into the whole protein sequence. For instance, look at the entry for the response regulator protein PhoB.
October 2015, David Goodsellhttp://doi.org/10.2210/rcsb_pdb/mom_2015_10