ompC mutants which allow growth on maltodextrins show increased channel size and greater voltage sensitivity

Misra and Benson [(1988) J. Bacteriol. 170, 3611-3617] showed that point mutations in the ompC gene can allow Escherichia coli to grow on maltotriose in the absence of LamB. This report shows that these mutants produce OmpC porins with increased single channel conductance compared to the wild type. The mutants showed similar voltage dependence to each other and to PhoE by being totally closed at 200 mV. The wild type from various sources was largely insensitive to voltages below 200 mV and thus 6 point mutations at 3 sites appear to increase the voltage dependence of OmpC channels.