  A physical model for a structured tetrameric pore is studied. The pore is
modeled as a device composed of four subunits, each one exhibiting two possible
states (open and closed). The pore is located within a membrane that separates
two reservoirs with ionic solutions. All variables of the model follow physical
dynamical equations accounting for the internal structure of the pore, derived
from a single energy functional and supplemented with thermal noises. An
extensive study of the resulting ionic intensity is performed for different
values of the control parameters, mainly membrane potential and reservoir ion
concentrations. Two possible physical devices are studied: voltage-gated
(including a voltage sensor in each subunit) and non-voltage-gated pores. The
ionic flux through the pore exhibits several distinct dynamical configurations,
in particular subconductance states, which indicate very different dynamical
internal states of the subunits. Such subconductance states become much easier
to observe in sensorless pores. These results are compared with available
experimental data on tetrameric K channels and analytical predictions.
