Vol. 176 No. 5, February 26, 2007. Pages 573–580.

In the original version of Fig. S1 B, the color layers corresponding to Che-MIIA and GFP-MIIB were accidentally misaligned, resulting in a 15-pixel shift from magenta to green. The corrected version of the figure was posted online on March 1, 2007, and also appears below.