Profilin is localized in the nucleus-associated microtubule and actin system and is evenly distributed in the cytoplasm of the green alga Micrasterias denticulata

Profilin is detected by means of immunoblotting in the green alga Micrasterias denticulata at a molecular mass of about 14 kDa with antibodies against celery root profilin, recombinant tobacco profilin, and recombinant birch profilin. Poly-L-proline purification of nk denticulata extracts leads to a single band at 14 kDa. By moans of immunoelectron microscopy first evidence is provided for the presence of profilin in a microtubule center associated with the migrating nucleus in high-pressure-frozen and freeze-substituted cells. Colocalization with a particular filamentous-actin aggregation in the same area suggests a role of profilin in the process of nuclear migration. Moreover staining is visible in several areas of the nucleus including the nucleolus, heterochromatin, and nuclear-pore complexes. An even distribution of profilin is found throughout the cytoplasm at the confocal-microscopy level as well as by immunogold labeling. Occasionally also areas at the surface of the chloroplast are stained.