Different Ca²⁺-sensitivities between the EF-hands of T- and L-plastins

Plastins are Ca(2+)-regulated actin-bundling proteins, and essential for developing and stabilizing actin cytoskeletons. T-plastin is expressed in epithelial and mesenchymal cells of solid tissues, whereas L-plastin is expressed in mobile cells such as hemopoietic cell lineages and cancer cells. Using various spectroscopic methods, gel-filtration chromatography, and isothermal titration calorimetry, we here demonstrate that the EF-hand motifs of both T- and L-plastin change their structures in response to Ca(2+), but the sensitivity to Ca(2+) is lower in T-plastin than in L-plastin. These results suggest that T-plastin is suitable for maintaining static cytoskeletons, whereas L-plastin is suitable for dynamic rearrangement of cytoskeletons.