The Cystic Fibrosis Transmembrane Conductance Regulator (CFTR), the protein implicated in cystic fibrosis (CF), has approximately 2,000 single mutations that cause dysfunction of the protein. Defective CFTR causes a thickening of mucus leading to infections, lowered quality...
The Cystic Fibrosis Transmembrane Conductance Regulator (CFTR), the protein implicated in cystic fibrosis (CF), has approximately 2,000 single mutations that cause dysfunction of the protein. Defective CFTR causes a thickening of mucus leading to infections, lowered quality of life and untimely death. Ireland, the country where these actions took place, has the highest CF birth rate. Vertex Pharmaceuticals created 3 drugs that restore activity of impaired CFTR, however these medications are expensive: Kalydeco, cost $300,000 a year per patient, a large sum of money for sick and vulnerable patients.
The objectives of these actions were as follows: (1) obtain pure, active CFTR and screen for conditions that generate high-resolution crystals (2) solve the high-resolution X-ray crystal structure of CFTR in absence and presence of CF medications (3) use structure-based drug design computer programs to develop medications that increase binding specificity, improve drug efficacy and decrease financial hardships. These results have the potential to positively impact the global economy by reducing CF costs, extend life expectancy, improve quality of life and lessen the burdens placed on their caretakers.
At the start of these actions, no structures existed for CFTR and we focused on X-ray crystallography. High-resolution crystal structures would give insights into the mode of action for CFTR while yielding clinically relevant details of the CFTR-drug interactions. Despite our exhaustive efforts to produce protein and the screening of tens of thousands of different crystallization conditions, CFTR remains resistant to crystal formation. Regrettably, we were not successful in the crystallization of CFTR. Cryogenic electron microscopy (CryoEM), is a lesser-established, alternative structural biology technique used to obtain structures. During these actions, 3 high-resolution CryoEM structures of CFTR were published by Jue Chenâ€™s group from Rockefeller University, USA, yielding information on its mode of activation. Additionally, the group of John Riordan from University North Carolina at Chapel Hill, USA, our collaborator on this project, published 2 low-resolution CryoEM structures of CFTR during these actions
CFTR was purified and standard quality control checks were performed with each new batch. Despite 2 years of purification and hundreds of crystallization trays set, CFTR remains resistent to crystallogenesis and no protein diffraction was detected and therefore no high resolution crystal structure of CFTR was obtained.
If successful, structure based drug design projects would have been a continuation of this work, but as there was no high resolution structure, the work is no longer in progress.