Isolation and physico-chemical properties of blood platelet alpha-actinin.

A procedure for the isolation of alpha-actinin from human blood platelets is described. Typical yields were 10-13 mg from 48 g of frozen platelets. The purified platelet alpha-actinin has many physico-chemical properties (molecular weight in native state, molecular weight in denaturing conditions, Stokes radius, ellipticities at 208 and 221 nm) similar to those of muscle alpha-actinins. However, in contrast to muscle alpha-actinins, it is composed of isoforms containing subunits of slightly different molecular weights and its effect on actin gelation is calcium-sensitive. These two characteristics are common to other known non-muscle alpha-actinins.