 In some cases, misfolding of the protein results in a loss of its usual function.For example, cystic fibrosis is caused by a defective cystic fibrosis transmembrane conductance regulator (CFTR) protein, and in amyotrophic lateral sclerosis / frontotemporal lobar degeneration (FTLD), certain gene-regulating proteins inappropriately aggregate in the cytoplasm, and thus are unable to perform their normal tasks within the nucleus.Because proteins share a common structural feature known as the polypeptide backbone, all proteins have the potential to misfold under some circumstances.