Sequence determination of low molecular weight salivary histidine-rich polypeptides from electroblots

Saliva contains six major cationic antifungal histidine-rich polypeptides (HRP) which are degraded by salivary proteases to smaller minor peptides. The primary structures of the minor peptides from one of these major HRPs, HRP-5, were elucidated in this study. Digestion of the HRP-5 substrate by human parotid saliva was followed by cationic polyacrylamide gel electrophoresis, electroblotting onto Whatman GF/C paper and gas-phase sequencing of Coomassie blue stained blots. A total of eight minor peptides were structurally analyzed. The smallest molecule characterized contained seven amino acid residues, suggesting that the technique was applicable for sequence determination of cationic peptides in the low molecular weight range.