When ligands bind to a specific subset of receptors, the ligands stabilize specific protein conformations, turning on (or off) molecular switches that control diverse cellular functions. For example, the binding of the breast cancer treatment tamoxifen is specific for the inactive conformation of the estrogen receptor - this locks the receptor in place, blocks the active conformation and prevents tumor growth.

"Our new findings suggest that we need to think not only about an ensemble of protein conformations, but also an ensemble of ligand binding orientations when we think about therapeutic compounds," Nettles said. "As the protein and ligand move together, each can have a unique affinity, and activity profile, which working together defines the signaling output."

Nettles is excited by the possibility the new study suggests of working with an ensemble of ligand conformations, perhaps combining one with anti-inflammatory properties - which play a role in cancer - with another that blocks tumor growth. "This would give you dual therapeutic activity, potentially doubling the effectiveness of the treatment," he said.

Nettles is also eager to find out whether the new study's findings apply to other ligand-protein pairs. "If ligand dynamics turn out to be a general feature of small molecule signaling," he said, "then our findings have the potential to transform how we think about chemical biology."

Source: Scripps Research Institute