A pinky promise explains a riboswitch puzzle

As we learn more about the complex process behind protein synthesis in cells, it’s become clearer that there are many players that contribute to the transcription and translation of DNA.

One of these players is the riboswitch, a short segment of RNA that sits at the rims of a messenger RNA. Upon binding of a small molecule ligand, the exposure of the riboswitch changes, affecting the protein expression. The guanidine-II riboswitch has a unique preference for an adenine ring over guanine — two of the four RNA bases — at the back of the binding pocket of the structure, which has remained unexplained.

Eble et al. used simulations and network analysis to discover the reason behind this strange preference.

They began with molecular dynamics simulations, which provide data on different conformations a molecule can adopt.

“This is a bit like the simulation method has been throwing at you a big haystack of data, and you try to sort that,” said author Christine Peter.

This is where the network analysis comes in: Researchers can observe how the RNA bases interact through hydrogen bonding and make sense of the patterns.

In the sea of data, they found the interlocking pinky-promise structure: an interaction that explains the preference for an adenine-adenine or adenine-guanine stack at the back of the binding pocket, something not seen before in crystallization data.

The network analysis they used for the riboswitch was something originally developed for protein analysis, so the fact that it could be adapted was promising to Peter and her team.

“The method of [adapting] the network analysis to the RNA — that’s really, for us, a novelty,” she said. “That’s something that we are really thrilled about — that it worked so well. We are really eager to develop this further.”

Source: “A kind of pinky promise: Chain interlocking in the guanidine-II riboswitch observed in atomistic simulations and network analysis,” by Franziska Eble, Leon Franke, and Christine Peter, Journal of Chemical Physics (2026). The article can be accessed at https://doi.org/10.1063/5.0346792 .

This paper is part of the Festschrift in honor of Gerhard Hummer: Molecular Machines, Membranes, and Mechanisms: The Physics of Life at Work Collection, learn more here .