Arginine uptake activity in E. coli cells expressing chlamydial AaxB and AaxC proteins. L-[2,3,4,5-3H]Arginine was added to suspensions of E. coli DEG0147 cells during 20 min incubations at 37°C. The relative radioactivity retained on filters is shown for the mean of three samples, with the corresponding standard deviations. The indicated genes were expressed from vectors pBAD/HisA (negative control), pDG479 (L2/434 aaxBC), pDG543 (L2/434 aaxB X128W-aaxC), pDG379 (C. pneumoniae aaxBC), and pDG558 (D/UW-3 aaxBC). Similar levels of radioactivity were measured in samples containing E. coli with pBAD/HisA and control reactions with no cells. One-way ANOVA was used to identify significant differences among the samples, with Dunnett's multiple comparison post-test. A significant difference in samples expressing C. pneumoniae aaxBC (relative to pBAD/HisA) is indicated by *, p ≤ 0.05; an extremely significant difference in samples expressing C. trachomatis D/UW-3 aaxBC is indicated by ***, p < 0.001.