I |
Protein production |
Complete absence of CFTR protein due to premature mRNA termination (nonsense or frame shift mutation) [18, 21, 22] |
G542X, W1282X, R553X, 621+G>T |
II |
Protein processing |
Inability of protein to localize to correct cellular location due to abnormal post-translational modifications [18] |
F508del, N1303K, A455E |
III |
Protein regulation |
Decreased activity of protein (chloride channel) in response to ATP due to abnormalities of the nuclear binding fold regions [18] |
G551D |
IV |
Protein conduction |
Frequency of flow of ions and channel opening duration are reduced though there is generation of chloride currents on stimulation with cAMP [18] |
R117H |
V |
Reduced amount of functional CFTR |
Stability of mRNA and/or mature protein is compromised [19, 20] |
A455E |
VI |
Normal amount of functional CFTR |
Enhanced turnover due to C-terminus abnormalities |
Q1412X |