Isolation and characterization of Physarum profilin.

A protein that functionally resembles mammalian and Acanthamoeba profilins, has been purified from Physarum plasmodia. Physarum profilin consists of a single polypeptide with a molecular weight of 11,000-13,000. It has an isoelectric point of 5.35-5.40 under denaturing conditions. The amino acid composition of this protein is similar to those of profilins isolated from other sources. Physarum profilin prolongs the process of actin polymerization in a concentration-dependent fashion. This effect is much stronger for Physarum G-actin than for muscle G-actin.