Conformational Changes of CFTR upon Phosphorylation and ATP Binding.

Area of Science:

• Structural biology
• Molecular biophysics
• Ion channel function

Background:

• The cystic fibrosis transmembrane conductance regulator (CFTR) is a crucial anion channel derived from ATP-binding cassette transporters.
• CFTR channel gating is intrinsically linked to phosphorylation and ATP hydrolysis.
• Previous studies elucidated the structure of CFTR in a dephosphorylated, ATP-free state.

Purpose of the Study:

• To determine the cryo-EM structure of zebrafish CFTR in its phosphorylated, ATP-bound conformation.
• To elucidate the structural rearrangements associated with CFTR channel opening.
• To understand the mechanism of ion permeation in CFTR.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was employed to determine the structure.
• High-resolution structure determination was achieved at 3.4 Å resolution.
• Comparative analysis of distinct CFTR conformations.

Main Results:

• The phosphorylated regulatory domain disengages from its inhibitory stance.
• Nucleotide-binding domains (NBDs) form a head-to-tail dimer upon ATP binding.
• The cytoplasmic pathway opens, unlike in other ABC transporters, while the extracellular pore mouth remains closed.

Conclusions:

• Phosphorylation and ATP binding induce significant structural changes that facilitate CFTR channel opening.
• The unique structural rearrangements highlight CFTR's distinct channel function.
• Local movements in transmembrane helices likely regulate ion access to the pore, even when NBDs are dimerized.