Purification and Partial Characterization of a Basic Protein from Pig Brain

A basic protein has been isolated from pig brain. The purification procedure consisted of repeated extractions with chloroform-methanol (2:1 v/v), 10% sodium chloride, and dilute hydrochloric acid. The pH 2.4 to 2.6 fraction obtained from the repeated acid extraction was further purified by pH and (NH 4 ) 2 SO 4 fractionation, Sephadex G-100 gel filtration, and chromatography on Amberlite IRC-50 with a gradient (5 to 20%) of guanidinium chloride. All of the fractions obtained by this purification procedure have been examined by starch gel electrophoresis. The homogeneity of the pig brain basic protein has been established by ultracentrifugation, starch gel electrophoresis, polyacrylamide gel electrophoresis, and end group analysis. Amino acid analysis performed on a complete acid hydrolysate of the protein indicated that the ratio of basic to acidic amino acids is greater than 1.5. An absence of cysteine and the presence of a high glycine and proline content have also been observed.