Wehave presented anew protein–proteindocking approach to model heterodimeric structures based on
the conformations of the monomeric units. The conventional modeling method relies on superimposing
two monomeric structures onto the crystal structure of a homologous protein dimer. The resulting
structure may exhibit severe backbone clashes at the dimeric interface depending on the backbone
dissimilarity between the target and template proteins. Our method overcomes the backbone clashing
problem and requires noa prioriknowledge of the dimeric structure of a homologous protein. Here we
used human Cystic Fibrosis Transmembrane conductance Regulator (CFTR), a chloride channel whose
dysfunction causes cystic fibrosis, for illustration. The two intracellular nucleotide-binding domains
(NBDs) of CFTR control the opening and closing of the channel. Yet, the structure of the CFTR’s NBD1–
NBD2 complex has not been experimentally determined. Thus, correct modeling of this heterodimeric
structure is valuable for understanding CFTR functions and would have potential applications for drug
design for cystic fibrosis treatment. Based on the crystal structure of human CFTR’s NBD1, we
constructed a model of the NBD1–NBD2 complex.