Selectivity changes in site-directed mutants of the VDAC ion channel: structural implications

Area of Science:

• Biophysics
• Molecular Biology
• Structural Biology

Background:

• The yeast mitochondrial outer membrane channel VDAC (voltage-dependent anion channel) plays a crucial role in cellular transport.
• Understanding the structural basis of VDAC's function is essential for deciphering mitochondrial physiology.

Purpose of the Study:

• To investigate the relationship between amino acid sequence and VDAC channel function.
• To identify key residues that determine the pore's selectivity and structural organization.

Main Methods:

• Site-directed mutagenesis was employed to alter 29 amino acid positions in the VDAC gene.
• Mutant VDAC channels were expressed in yeast and reconstituted into phospholipid bilayers for functional analysis.
• Electrophysiological techniques were used to assess channel selectivity and conductance.

Main Results:

• Mutations at 14 distinct sites resulted in significant changes in VDAC channel selectivity.
• These identified sites are localized to the protein's transmembrane segments, lining the aqueous pore.
• A model for the open state of VDAC was proposed, involving 12 beta-strands and one alpha-helix per polypeptide.

Conclusions:

• Specific amino acid residues critically influence the charge selectivity of the VDAC pore.
• The study provides insights into the structural architecture of the VDAC channel.
• The proposed model aids in understanding VDAC's role in mitochondrial function.