A collaborative study between the laboratories of Jeff Peng at the University of Notre Dame and Felicia Etzkorn at Virginia Tech has discovered an important element of how Pin1, an enzyme involved in cell division, does its job. Their report, “Stereospecific gating of functional motions in Pin1,” appeared recently in the online edition of the Proceedings of the National Academy of Sciences. Prof. Peng is a Concurrent Professor of Physics.
Pin1 controls the proteins that start cell division by changing the shape of their peptide bonds. The enzyme consists of two loosely-connected domains, or structural modules – a catalytic domain and a Trp-Trp (WW) domain. When Pin1 binds a target peptide bond, communication between its two domains increases, but the molecular basis for this cross-protein communication was unclear.
Using nuclear magnetic resonance (NMR) spectroscopy, the researchers discovered that Pin1 undergoes different changes in dynamics when it binds different shapes. When Pin1 binds the cis-shape, its internal dynamics decreases more dramatically than when it binds the trans-shape. The sites showing dynamic changes define an internal conduit linking the two domains, providing for the cross-protein communication.
“The results suggest that the binding of different shapes turns on different dynamics relevant for intra-molecular communication,” Peng says. “We knew that cis versus trans binding gave rise to different behavior, but we didn’t know how. Now we know that the moving parts of the protein are critical.”
Peng’s lab carried out the NMR experiments on Notre Dame’s high-field NMR spectrometers, using special ligands, locked in the cis versus trans shapes, that were designed by Etzkorn’s lab. The equipment provided the necessary high sensitivity and resolution to collect meaningful dynamics data – capturing the protein in action as on video, rather than the stop-action images previously available.
The Pin1 study also contributes to the understanding of allostery, one of the basic challenges in fundamental protein biophysics. Allostery is the phenomenon whereby ligand binding at one protein site is effectively communicated to another distinct site, and the Pin1 results show that protein dynamics may play a role.
Other authors include Andrew Namanja, who is now a postdoctoral associate at the Beckman Research Institute of the City of Hope, and Kimberly Wilson, a graduate student in the Peng Lab, as well as members of Etzkorn’s lab.