Effect of charges in wildtype and mutant HlyA on the single-channel conductance.

Abstract

<p>The single-channel conductance of the HlyA, HlyA_Δ71–110, and HlyA_Δ264–286 channels is shown as a function of the KCl concentration in the aqueous phase. The solid lines represent the fit of the single-channel conductance data with eqn. <i>G(c) = G₀⋅c₀⁺</i> (a combination of eqs. (3–5 and 7) assuming the presence of negative point charges within the channel (for HlyA: 2.3 negative charges, <i>q = </i>−3.68×10^–19 As; for HlyA_Δ71–110∶1.7 negative charges, <i>q</i> = -2.72×10^–19 As; for HlyA_Δ264–286∶2 negative charges, <i>q = </i>-3.2×10^–19 As) and assuming a channel diameter of 2 nm, 1.4 nm, and 1.6 nm for HlyA, HlyA_Δ71–110, and HlyA_Δ264–286, respectively. <i>c</i>, concentration of the KCl solution in M (molar); <i>G</i>, average single-channel conductance in nS (nano Siemens, 10^–9 S); <i>G₀</i>, specific single-channel conductance in the absence of negative point charges given in pS/M. The broken, dotted, and fractured (straight) lines show the single-channel conductance of the HlyA, HlyA_Δ264–286, and HlyA_Δ71–110 channels in the absence of point charges and correspond to linear functions between channel conductance and bulk aqueous concentration (eqn. (7); <i>G(c) = G₀⋅c</i>).</p