  Translocation of a single stranded DNA through genetically engineered
$\alpha$-hemolysin channels with positively charged walls is studied. It is
predicted that transport properties of such channels are dramatically different
from neutral wild type $\alpha$-hemolysin channel. We assume that the wall
charges compensate the fraction $x$ of the bare charge $q_{b}$ of the DNA piece
residing in the channel. Our prediction are as follows (i) At small
concentration of salt the blocked ion current decreases with $x$. (ii) The
effective charge $q$ of DNA piece, which is very small at $x = 0$ (neutral
channel) grows with $x$ and at $x=1$ reaches $q_{b}$. (iii) The rate of DNA
capture by the channel exponentially grows with $x$. Our theory is also
applicable to translocation of a double stranded DNA in narrow solid state
nanopores with positively charged walls.

Subcellular Processes;Soft Condensed Matter