Isolation and partial sequence of goat spleen prothymosin alpha

Goat prothymosin alpha, a highly acidic polypeptide of pI3.5, 109 amino acid residues, has been isolated from lymphoid and non-lymphoid tissues of young female goats. Unlike rat, murine and porcine prothymosins alpha, goat prothymosin alpha appears at a higher concentration in the spleen compared with the thymus. The sequence of segments of the polypeptide involving known mutations has been determined, by automatic sequencing of its tryptic peptide fragments. The acidic amino acid-rich segment in the middle of the molecule, including residues 49-83, has not been sequenced. Goat prothymosin alpha closely resembles bovine prothymosin alpha, with only one substitution, proline for alanine at position 85. It also resembles human prothymosin alpha, with only three substitutions. It differs more significantly from rat and murine prothymosins alpha, by two deletions and three substitutions. The results show the highly conserved nature of the molecule, with substitutions at given positions only.