The structure of the humanCFTR’sNBD2 wasmodeledusing the
crystal structure of the human CFTR’s NBD1 as a template (PDB
code: 1XMI) [11]. The sequence alignment, giving a sequence
identity of 24.8% and a similarity of 43.6% between NBD1 and
NBD2, is shown inFig. 1. Before modeling, the bound ATP was
removed from the template. Based on the crystal structure of
NBD1, the MODELLER program[25] was used to generate the
three-dimensional structure of NBD2. Finally, AMBER force field
minimization[26] was performed to optimize the constructed
NBD2 model.