High Quality Content by WIKIPEDIA articles! Gelsolin is an actin-binding protein that is a key regulator of actin filament assembly and disassembly. Gelsolin is one of the most potent members of the actin-severing gelsolin/villin superfamily, as it severs with nearly 100% efficiency. Gelsolin is located intracellularly (in cytosol and mitochondria) and extracellularly (in blood plasma).