How Do Bacteria “See” Molecules Inside Themselves?

Abstract

RNA, like its close cousin DNA, is used to store information in the cell. Unlike DNA, RNA is really good at folding up into interesting shapes, which also makes it good at lots of other important jobs. Some kinds of RNA, called riboswitches, can sense what is going on inside a cell. Each riboswitch fits a specific small molecule. When the riboswitch and small molecule interact, this changes what the cell does. For example, if the small molecule is harmful, the cell might start making a protein that will get rid of it. Recently, scientists discovered some riboswitches that look very similar to each other but recognize very different small molecules. We used a technique called X-ray crystallography to get pictures of these riboswitches, and we saw how changing just one piece of the riboswitch changed which small molecule it recognized. This shows us how RNA can gain new functions as an organism evolves.