by Claire Naylor, Product Manager, HexAuFoil
I had the pleasure of sitting down for a conversation with Dr. Bharat Reddy, a Senior Scientist at Rectify Pharmaceuticals, to learn more about the exciting first published commercial use of our HexAuFoil® ultra-small hole gold-on-gold grids.
You can watch the full conversation here.
Enhancing drug discovery with structural biology at Rectify Pharmaceuticals
The team at Rectify Pharmaceuticals are focused on the development of positive function modulators (PFMs), small molecule therapeutics that restore and enhance membrane protein function to address the underlying cause of serious diseases. Rectify’s PFMs have potential to modulate the activity of wild-type and mutated membrane bound proteins, a historically difficult challenge with a small molecule approach. They are investigating therapeutics for treatment of rare and common diseases, including liver, cardio-renal-metabolic, and neurodegenerative diseases.
Rectify leverages cryo-EM for structural validation and optimization of PFMs. It allows the team to visualize how potential drug candidates interact at the atomic level with their protein targets. This information is essential for both binding specificity and toxicity assessments, streamlining the process of refining molecules that bind effectively without adverse effects.
HexAuFoil in action: Resolving the bile salt export pump (BSEP) structure
Rectify’s recent publication marked the first commercial use of HexAuFoil grids in cryo-EM. The focus of this work was structural studies around the bile salt export pump (BSEP), a liver-based protein that plays a crucial role in bile regulation. In particular, they are investigating BSEP dysfunction in primary sclerosing cholangitis (PSC). With HexAuFoil grids, Rectify has been able to gain new insights into how PFMs interact with BSEP, helping to identify promising therapeutic candidates.
Cryo-EM enables the precise differentiation between correctors, which restore protein function, and inhibitors, which could potentially interfere with it. The high resolution achieved with HexAuFoil grids allowed the team to screen for and eliminate compounds that might pose toxicity risks due to BSEP’s known promiscuity in binding multiple drugs.
What has HexAuFoil enabled for this project?
Switching from UltraFoil to HexAuFoil grids has delivered almost a half-angstrom improvement in resolution. This leap in quality stems from several factors in HexAuFoil’s design and construction, including its hexagonal array of ultra-small 300 nm holes and the enhanced stability these grids provide.
- Reduced Motion: HexAuFoil grids minimize image movement, a critical factor in improving resolution and achieving clearer structural data. Dr. Reddy noted that with these grids, individual images showed almost no motion, greatly enhancing the quality of the reconstructions.
- Optimized Sample Orientation and Consistent Ice Thickness: The thin flat film and densely-packed small holes of HexAuFoil grids ensure samples sit in an even distribution with no orientation preference. Additionally, they deliver uniformly thin ice which is essential for consistent imaging quality across the grid. HexAuFoil allows for uniform imaging across datasets, simplifying model building and reducing noise in the final maps.
- Increased Imaging Throughput: The enhanced stability and densely-packed hexagonal design of HexAuFoil grids also enable faster data collection. Dr. Reddy reported achieving an impressive 800-1000 images per hour, depending on the setup.
- Clearer Image Reconstructions: HexAuFoil grids have been especially beneficial in visualizing lipid regions in membrane proteins, which are often obscured using traditional grid supports. By providing less noisy images for these regions, HexAuFoil grids have allowed for a more accurate interpretation of target-bound PFMs at Rectify.
The Future of BSEP and Beyond
Encouraged by their success, Rectify Pharmaceuticals is now integrating HexAuFoil grids across all membrane protein projects. These new structural insights have informed the development of a dual-targeted PFM targeting BSEP and ABCB4, which is advancing towards clinical development. These PFMs, which have shown promising interactions in cryo-EM structures in the region of 2.5 Å resolution, are anticipated to be the foundation of future therapeutic candidates targeting bile-related diseases.
Watch the full interview
