Here, we focus on two case studies: the CFTR protein, which is responsible for chloride ion flux and whose mutations cause cystic fibrosis (Devidas and Guggino 1997), and the transmembrane protein YddG, which is found in bacteria and is involved in the export of aromatic amino acids (Tsuchiya et al. 2016). The gene discussed is CFTR; the disease is cystic fibrosis.