Gelsolin, a protein of leukocytes, platelets, and other cells, severs actin filaments in the presence of submicromolar calcium, thereby solating cytoplasmic actin gels. A gelsolin variant with 23 more N-terminal amino acids is a plasma component probably involved in the clearance of actin, the most abundant human protein, from the circulation. Gelsolin is located in 9q34. Plasma and cytoplasmic gelsolins are encoded by a single gene and contain a duplicated actin-binding domain.