Magnesium-sensing riboswitches in bacteria.

All living organisms require mechanisms for coordination of intracellular metal concentrations. Many types of metal-sensing regulatory proteins have been described previously. Data in recent years have revealed that posttranscriptional mechanisms are also utilized for control of metal ion homeostasis in bacteria. In particular, two classes of RNA structural elements have been discovered to coordinate magnesium-induced structural transitions with expression levels of downstream genes. We discuss these types of regulatory RNAs herein and compare them to other classes of riboswitches that respond instead to small organic metabolites.