Figure 9. Relationship between the permeability of extracellular organic (kosmotropic) anions and their mean diameters, in wild-type and T338 mutant CFTRs.

Permeability ratios (P_X/P_Cl) for formate, acetate, propanoate, pyruvate, methane sulphonate and gluconate were taken from Table 1; their ionic diameters are as calculated previously (Linsdell & Hanrahan, 1998). In each case the data have been fitted using eqn (2) (see Methods), giving estimates of the functional pore diameter (d) of 0.535 nm for wild type, 0.615 nm for T338A, 0.505 nm for T338S, 0.503 nm for T338N and 0.530 nm for T338V. Anions examined (in order of increasing diameter) were: formate, acetate, propanoate, pyruvate, methane sulphonate and gluconate.