Capturing the Intermediate State of Riboswitch-ligand Interaction

Using X-ray Free Electron Laser

Yun-Xing Wang, Ph.D.

Principal Investigator,

National Cancer Institute

NIH, Frederick, MD

Abstract:

In the genetic regulation by riboswitch RNAs, ligand binding to the aptamer domain triggers a signal to the downstream expression platform. A complete understanding of the structural basis for this mechanism requires the ability to study structural changes over time. With the application of serial femtosecond crystallography (SFX) and an X-ray free electron laser (XFEL), advances have been made in both time-resolved crystallography and riboswitch biology. A ligand-triggered real time crystallography has led to structure determination of the adenine riboswitch aptamer domain during the course of a four-state interaction involving two apo, an intermediate, and the final bound states. These structures serve as the strong proof of the four-state reaction kinetics model and illustrate the structural basis for signal transmission. Moreover, a polymorphic phase transition was observed when the RNA molecules were fully converted to the bound state in crystals. These results demonstrate the utility of ligand-triggered real time crystallography to study structural transitions in crystallo, including those involving large conformational changes. General implications of ligand-triggered real time crystallography will also be discussed.

Time: 16:30--17:30 pm, April 7th, 2017 (Friday)

Venue: New Biology Building, Room 143

Host: Xianyang Fang