We started with ABLE, a simple helical bundle that Nick Polizzi had designed as a postdoc to bind the drug apixaban (https://pmc.ncbi.nlm.nih.gov/articles/PMC7526616/) with high specificity compared to analogs. But could it do more? Enter crystallographic fragment screening...
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ABLE turned out to be a generalist, binding 43 fragments in two distinct conformations.
(side note, Nick and Justin Biel started this as COVID hit... but it paused until Lena picked it back up!)
ABLE->FABLE generalist to a specialist sensor with 100-fold turn-on fluorescence enhancement!
- Mutagenesis confirmed Asp49 as the essential active site residue
- Disrupting key orienting H-bonds also eliminated activity
- kcat/KM for analogs scaled with the electron-withdrawing nature of leaving groups
We think this mimics how evolution explores generalist binding sites to generate new functions.
Link to preprint: https://www.biorxiv.org/content/10.1101/2025.01.30.635804v1
We welcome feedback!