5- and 4′-Hydroxylated flavonoids affect voltage gating of single alpha-hemolysin pore

Molecular mechanisms of the influence of flavonoids on the voltage gating of a single alpha-hemolysin channel in planar lipid membranes are studied. It is shown that the addition of flavonoids hydroxylated in position 5 of the A-ring and in position 4′ of the B-ring into bilayer bathing solution shifts the voltage dependence of channel switching from high- to low-conductance states to voltages nearer zero. It is concluded that the effect is likely to be attributed to a specific interaction of at least three flavonoid molecules with the voltage sensor of an alpha-hemolysin pore. Possible flavonoid binding sites and identification of amino acid residues included into the voltage sensor domain of the alpha-hemolysin channel are discussed.

Research Highlights
► Flavonoids hydroxylated in position 5 of the A-ring and in position 4' of the B-ring shifts the voltage dependence of alpha-hemolysin channel switching from high- to low-conductance states to voltages nearer zero.
► Introduction of flavonoids does not alter the conductance, lifetime and the selectivity of low conductance state of alpha-hemolysin pore.
► The effect is attributed to a specific interaction of at least three flavonoid molecules with the voltage sensor of single alpha-hemolysin pore.
► Comparison of the distances between the polar amino acid residues in the same positions of neighboring protomers and between 5-OH and 4'-OH-groups of the flavonoid molecule allows speculating that the most appropriate candidate for a possible flavonoid binding site is Thr129.