FIG 11.

Model of pore lumen of colicin U and Ia. (A) Our proposed model of the inner profile of colicin U. The profile is deduced from the results of pore filling by NEs. Molecules of glycerol (0.62 nm) can enter the pore without limitations from both sides of the membrane, whereas the size of arabinose (0.68 nm diameter) is comparable to the pore diameter. Sorbitol molecules (0.78 nm) can only occupy the pore entrances, while the bigger molecules, such as maltose (1.0 nm), cannot enter the pore at all. (B) The geometrical profile of the colicin Ia pore exhibits a strikingly asymmetrical shape. The parameters were taken from Krasilnikov and colleagues (54).