THE AMINO-ACID-SEQUENCE OF A BOAR TRANSITION PROTEIN-3

The boar transition protein 3 (TP3) was extracted with acid from the isolated late spermatid nuclei or directly from the testes, fractionated with trichloroacetic acid, and reduced and carboxymethylated (RCM-). RCM-TP3 from the nuclei was purified by HPLCs on Nucleosil 300 7Cl8 and Hitachi #3057, and that from the testes, by ion-exchange chromatography on CM-Sephadex C-25 and HPLCs on Nucleosil 300 7Cl8 and Chemcosorb 7C8. The two TP3 preparations were identical in acid-urea- and SDS-gel electrophoretic mobilities and amino acid composition. The primary structure of TP3 was determined by manual Edman degradation of the peptides obtained by lysyl endopeptidase-digestion or by alpha-chymotrypsin-digestion of RCM-TP3 from the testes, and by automated Edman degradation of it. Boar TP3 is a basic protein of 76 residues: H-AKVTEKSWQPQTTSTKRWKKRKTPSQPRSR-GKVRKIYKKVKRPLHVCSRKKYSPKVITTSRRQKRARRANKFETIP-OH, and it shows 27% homology with boar TP1. TP3 is composed of an N-terminal region (1-19) having two characteristic tryptophan residues (8 and 18) which is absent in the known TP1 group, and a C-terminal region (20-76) having a close resemblance to boar TP1.