A high molecular weight actin-binding protein was isolated from the Physarum polycephalum plasmodia. The protein ( HMWP ) shares many properties with other high molecular weight actin-binding proteins such as spectrin, actin-binding protein from macrophages, and filamin. It has a potent activity to cross-link F-actin into a gel-like structure. Its cross-linking activity does not depend on calcium concentrations. Hydrodynamic studies have revealed that the protein is in the monomeric state of a polypeptide chain with molecular weight of approximately 230,000 in a high ionic strength solvent, while it self-associates into a dimer under physiological ionic conditions. Electron microscopic examinations of HMWP have shown that the monomer particle observed in a high ionic strength solvent is rod shaped with the two-stranded morphology very similar to that of spectrin. On the other hand, under physiological ionic conditions, the HMWP dimer shows the dumb-bell shape with two globular domains connected with a thin flexible strand.
Isolation and characterization of a high molecular weight actin-binding protein from Physarum polycephalum plasmodia.
K Sutoh, M Iwane, F Matsuzaki, M Kikuchi, A Ikai; Isolation and characterization of a high molecular weight actin-binding protein from Physarum polycephalum plasmodia.. J Cell Biol 1 May 1984; 98 (5): 1611–1618. doi: https://doi.org/10.1083/jcb.98.5.1611
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