Table 2.

Characteristics of LacY wild-type and mutant preparations

CharacteristicWild-type LacYC154G LacYE325A LacY
Particles per μm2≈4,500≈3,500≈3,500
Peak current, pA960 ± 190102 ± 67 211 ± 50 
Q, pC96 ± 195 ± 24.4 ± 0.4
  • The number of particles per μm2 was estimated from freeze–fracture images (Fig. S2 and Fig. S3). The peak currents refer to the transients after 50 mM lactose concentration jumps at pH 7.6. Conditions are as described in Figs. 1 and 4. The total translocated charge (Q) is obtained from numerical integration of the currents. Charge translocation per turnover of the wild-type was estimated by using the current of 960 pA and an estimated turnover rate of 10 s−1.