Actin in Mammalian Lens

Abstract

Evidence is provided that one of the protein components of the water-soluble fraction of the calf lens binds specifically to DNase I. On the basis of this property, the polypeptide could be purified by applying DNase I affinity chromatography. Concomitantly a protein of 55,000 MW and a rather large amount of .alpha.-crystallin copurify with this polypeptide, which has a 42,000 MW. Highly purified 42,000 MW protein was obtained by extraction of the water-insoluble fraction of the calf lens with 2-{[tris(hydroxymethyl)methyl]amino}ethanesulfonic acid followed by gel filtration. Amino acid analyses, peptide mapping and EM show that the protein obtained from both lens fractions is identical to non-muscle actin. Furthermore, the amino acid composition of the 55,000 MW protein is identical to hog stomach skeletin and very similar to calf brain desmin.