Abstract
Two highly acidic protein preparations (chick brain acidic protein: CBA I and II) were obtained from chick brain by extraction with 55% saturated ammonium sulfate, followed by DEAE-Sephadex A-50 column chromatography and Sephadex G-75 gel chromatography. Both proteins migrated with bromphenol blue (BPB) marker dye on 7.5% polyacrylamide gel disc electrophoresis. CBA I gave essentially a single band on 7.5% polyacrylamide gel electrophoresis, but showed slight contamination on 15% gel. On the other hand, CBA II was homogeneous on both 7.5% and 15% polyacrylamide gel disc electrophoresis. The yields of CBA I and CBA II were about 40mg and 700mg, respectively, from 9kg of chick brain. CBA II showed a characteristic absorption spectrum in the region from 250 to 280nm, presumably due to phenylalanine residues in the protein. Molecular weights were estimated to be 14, 500 for CBA I and 16, 000 for CBA II by SDS-polyacrylamide gel electrophoresis. One major N-terminal amino acid residue in addition to two minor ones was detected for CBA I by the dansylation method, but no N-terminal residue could be detected in CBA II. Amino acid compositions indicated that the two protein preparations were rich in acidic and hydrophobic amino acid residues. The peptide maps of tryptic peptides were different. CBA I cross-reacted with the antiserum against bovine S-100 protein, but CBA II did not. Based on these results, it was concluded that CBA I contained S-100 protein and was different from CBA II. In addition, both proteins were compared with two highly acidic proteins purified from bovine brain (PAP I and PAP II). CBA I was different from PAP I, but CBA II was virtually identical with PAP II in amino acid composition.
