Figure 4.

The Sec translocon diffuses much more slowly than a typical IMP. (A) Histogram showing the measured apparent diffusion coefficients (D_app) for SecE and PgpB. Median depicted as black line. Data shown on a log₁₀ scale. KS tests indicated a p value of <0.0001 between SecE (n = 878 tracks) and PgpB (n = 730 tracks) and a p value of 0.030 between SecE and BamA. (B) Complementary cumulative probability distributions of single-step square displacements for IMP constructs. The black lines represent the best fits to the sum of two exponentials. (C and D) Dependence of the apparent diffusion coefficients on (${\mathrm{D}}_{\text{app}}^{\text{slow}}$) on lag time. The individual apparent diffusion coefficients for the slow (C) and fast (D) modes are shown as a function of inverse lag time. The data points and error bars are derived from the average and SE of the mean values determined from experimental replicates, respectively. The D_true values extracted from the y intercepts are annotated on the figures, and the number in parentheses represents the uncertainty in the least significant digit as given by the SE of the mean from experimental replicates. (C) R² values for each fit are 0.9947 and 0.9943 for SecE and PgpB, respectively. An extra sum-of-squares F test to compare the y intercepts was performed and yielded a p value of 0.031 for the ${\mathrm{D}}_{\text{true}}^{\text{slow}}$ of SecE and PgpB. (D) R² values for each fit are 0.9715 and 0.9828 for SecE and PgpB, respectively. An extra sum-of-squares F test to compare the y intercepts was performed and yielded a p value of 0.0003 for the ${\mathrm{D}}_{\text{true}}^{\mathrm{f}\text{ast}}$ of SecE and PgpB. To see this figure in color, go online.