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Biophys J, December 2002, p. 3001-3011, Vol. 83, No. 6
Laser Laboratory for Fast Reactions in Biology, Department of Biochemistry, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Ramat Aviv 69978, Israel
The PSST program (see accompanying article)
utilizes the detailed structure of a large-pore channel protein as the
sole input for selection of trajectories along which negative and
positive ions propagate. In the present study we applied this program
to reconstruct the ion flux through five large-pore channel proteins (PhoE, OmpF, the WT R. blastica
general diffusion porin and two of its mutants). The conducting
trajectories, one for positive and one for negative particles, are
contorted pathways that run close to arrays of charged residues on the
inner surface of the channel. In silico propagation of the charged
particles yielded passage time values that are compatible with the
measured average passage time of ions. The calculated ionic mobilities
are close to those of the electrolyte solution of comparable
concentrations. Inspection of the transition probabilities along the
channel revealed no region that could impose a rate-limiting step. It
is concluded that the ion flux is a function of the whole array of
local barriers. Thus, the conductance of the large-pore channel protein
is determined by the channel's shape and charge distribution, while
the selectivity also reflects the features of the channel's vestibule.
Biophys J, December 2002, p. 3001-3011, Vol. 83, No. 6
© 2002 by the Biophysical Society 0006-3495/02/12/3001/11 $2.00
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