Observations and implications on the migration of calmodulin in a two-dimensional gel system

These studies investigated the effect of calcium on the migration of calmodulin in a two‐dimensional (2‐D) gel system. As reported for one‐dimensional gels, calmodulin migrates on 2‐D gels primarily as a 21 kDa protein in the presence of 0.1 mM EDTA, and as a 15 kDa protein in the presence of 0.1 mM CaCl2. However, under basal conditions (i.e., neither EDTA nor calcium added to the bùffer system), calmodulin migrates on a 2‐D gel as a doublet of 20.3 and 18.7 kDa. These results suggest that sufficient residual calcium may be present in one (or more) of the standard laboratory reagents used in running 2‐D gels to produce this unique migration pattern for calmodulin. These results may also have implications for the migration of other proteins on 2‐D gels.