A molecular dynamics study of the CFTR nucleotide binding domains interaction.

The cystic fibrosis transmembrane conductance regulator (CFTR), the dysfunctional protein in cystic fibrosis, contains two transmembrane domains, two nucleotide-binding domains (NBDs), and a regulatory domain. Opening of the pore have been linked to the ATP-driven tight dimerisation of NBD. We have studied the NBD1-NBD2 interactions on wild type and cystic fibrosis-related mutations by steered molecular dynamics simulations (SMD). A fully solvated dimer, including the two bound ATPs, was separated by pulling one monomer with an external, increasing force. Interestingly, the force needed to break the mutated (G511D) dimer is significantly smaller than in the wild type case. The effect of a CFTR potentiator, the genistein, has also been tested by repeating the SMD simulations with the small molecule docked at the interface between the two NBD domains. To test the validity of our results we have repeated the separation process for different simulation lengths and force strengths. The amount of distortion on the pulled NBD domain has also been studied. This work is partially supported by the Italian Cystic Fibrosis Foundation (Prog FFC #2/2008), with the contribution of "Mille bambini a Via Margutta"onlus"Blunotte", "Lega Italiana FC Toscana"