Interdomain but not intermolecular interactions observed in CFTR channels

Gating of the cystic fibrosis transmembrane conductance regulator (CFTR) ch annels requires interdomain and/or intermolecular interactions involving di fferent parts of the protein, yet the exact nature of those interactions re mains unclear. In this study we report that treating wild type CFTR-express ing cells with oxidizing agents results in a significant reduction in the g el mobility of the protein indicative of the formation of disulfide bonds. In contrast, mutant CFTR channels in which cysteine residues in both nucleo tide binding domains (NBDs) were mutated to serine, showed little change in gel mobility in oxidizing conditions. Mutation of the two cysteine residue s in either the first or the second NBD alone also eliminates the change in gel mobility in oxidizing conditions. Wild type channels treated with oxid izing agents did not appear to form disulfide bonds with other proteins, su ggesting that the close association that allows the formation of disulfide bonds occurs only within single proteins and not between separate channels interacting in a multimer. (C) 2001 Academic Press.