Comparison of interphase D. discoideum cells. GFP-MHCK-A (A), GFP-MHCK-B (B), and GFP-MHCK-C (C) are expressed in Ax2 cells. GFP-myosin II (M) is expressed in myosin II null cells. Scale bar equals to 5 μm. Quantification of the increased accumulation of GFP-proteins in the cortex is obtained by line-scans of the fluorescent intensity profiles across the center of cells (middle row). The x-axis is the scanning coordinate in a unit of μm, and the y-axis is the fluorescence intensities in an arbitrary unit. Interphase cells moving in the upward direction show that GFP-MHCK-A localizes transiently to the anterior pseudopod (A, bottom), while GFP-MHCK-C and GFP-myosin II stay in the posterior region of the cells (C and M, bottom, respectively). GFP-MHCK-B, on the other hand, is homogeneously cytosolic (B, bottom). The brighter cells expressing any of these GFP constructs sometimes display intense fluorescent spots (as in A, top and bottom, and B, bottom) that are likely non-physiological aggregates of the overexpressed protein, as discussed previously . A time-lapse movie in Quicktime format illustrating the anterior localization behavior of MHCK A is available as an additional file (see additional file 1).