Deletion of beta-strands 9 and 10 converts VDAC1 voltage-dependence in an asymmetrical process

Voltage-dependent anion selective channel isoform1 maintains the
permeability of the outer mitochondrial membrane. Its voltage-gating
properties are relevant in bioenergetic metabolism and apoptosis. The
N-terminal domain is suspected to be involved in voltage-gating, due to
its peculiar localization. However this issue is still controversial. In
this work we exchanged or deleted the beta-strands that take contact
with the N-terminal domain. The exchange of the whole hVDAC1 beta-barrel
with the homologous hVDAC3 beta-barrel produces a chimeric protein that,
in reconstituted systems, loses completely voltage-dependence. hVDAC3
beta-barrel has most residues in common with hVDAC1, including V143 and
L150 considered anchor points for the N-terminus. hVDAC1 mutants
completely lacking either the beta-strand 9 or both beta-strands 9 and
10 were expressed, refolded and reconstituted in artificial bilayers.
The mutants formed smaller pores. Molecular dynamics simulations of the
mutant structure supported its ability to form smaller pores. The mutant
lacking both beta-strands 9 and 10 showed a new voltage-dependence
feature resulting in a fully asymmetric behavior. These data indicate
that a network of beta-strands in the pore-walls, and not single
residues, are required for voltage-gating in addition to the N-terminus.
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