RT Journal Article
SR Electronic
T1 The gating charge should not be estimated by fitting a two-state model to a *Q-V* curve
JF The Journal of General Physiology
JO J Gen Physiol
FD Rockefeller University Press
SP 575
OP 578
DO 10.1085/jgp.201311056
VO 142
IS 6
A1 Bezanilla, Francisco
A1 Villalba-Galea, Carlos A.
YR 2013
UL http://jgp.rupress.org/content/142/6/575.abstract
AB The voltage dependence of charges in voltage-sensitive proteins, typically displayed as charge versus voltage (Q-V) curves, is often quantified by fitting it to a simple two-state Boltzmann function. This procedure overlooks the fact that the fitted parameters, including the total charge, may be incorrect if the charge is moving in multiple steps. We present here the derivation of a general formulation for Q-V curves from multistate sequential models, including the case of infinite number of states. We demonstrate that the commonly used method to estimate the charge per molecule using a simple Boltzmann fit is not only inadequate, but in most cases, it underestimates the moving charge times the fraction of the field.