Solution structure of the integral human membrane protein VDAC-1 in detergent micelles

The voltage- dependent anion channel ( VDAC) mediates trafficking of small molecules and ions across the eukaryotic outer mitochondrial membrane. VDAC also interacts with antiapoptotic proteins from the Bcl- 2 family, and this interaction inhibits release of apoptogenic proteins from the mitochondrion. We present the nuclear magnetic resonance ( NMR) solution structure of recombinant human VDAC- 1 reconstituted in detergent micelles. It forms a 19- stranded beta barrel with the first and last strand parallel. The hydrophobic outside perimeter of the barrel is covered by detergent molecules in a beltlike fashion. In the presence of cholesterol, recombinant VDAC- 1 can form voltage- gated channels in phospholipid bilayers similar to those of the native protein. NMR measurements revealed the binding sites of VDAC- 1 for the Bcl- 2 protein Bcl-x(L), for reduced beta-nicotinamide adenine dinucleotide, and for cholesterol. Bcl-x(L) interacts with the VDAC barrel laterally at strands 17 and 18.