Altered actin distribution in GFP-YopE expressing cells. (A) Induced GFP-YopE expressing cells were allowed to sit on glass coverslips, fixed and stained with actin-specific mAb Act 1–7 followed by Cy3-labeled anti-mouse IgG. Images are confocal sections. Note that cells expressing large amounts of the GFP fusion have visibly less cortical actin. Examples of intensity profiles across cells that express large amounts GFP-YopE (1, 2) or no visible GFP-YopE (3, 4) are shown. Scale bar, 10 μm. (B) Intensity profiles across cells stained with actin-specific antibody. Control cells are induced cells that do not express GFP-YopE. The fluorescence intensity was determined for 30 cells from two independent preparations and the distance between the maxima at the cell cortex normalized. Shown is the average ± standard deviation. For simplicity, error bars are depicted in one direction only. *P < 0.05, Student's t-test. (C) Relative F-actin content of vegetative cells as determined by TRITC-phalloidin staining. Values were normalized to the total protein content of the sample. Unaltered total actin amounts were verified by Western blotting of total cell lysates. (5 μg of total protein) probed with mAb Act1-7. Control cells are non-induced cells carrying the GFP-YopE plasmid. Data are average ± standard deviation of 6 independent determinations. *P < 0.05, Student's t-test.