A cDNA containing coding information for buforin I (toad stomach antimicrobial peptide) was identified by PCR. The cloned cDNA codes for total 128 amino acids, contains buforin I, a single copy in the N-terminal region. Nucleotide sequence analysis of corresponding cDNA revealed that it shows significant homology with histone H2A, a replication-dependent histone of which expression of mRNAs is tightly coupled with DNA synthesis and involves both transcriptional and post-transcriptional mechanisms. Therefore, it is postulated that there exists a regulation mechanism to convert toad histone H2A.1 to buforin I that is also coupled with the cell cycle. A cDNA corresponding to TSAP (toad skin antimicrobial peptide) was also isolated using 3'-RACE and library screening. The cloned cDNA codes for total 102 amino acids, and TSAP is composed of 95 amino acids and 7 amino acids as putative signal sequence. Nucleotide sequence analysis of cloned cDNA shows homology with cysteine proteinase inhibitors, especially family 1 stefins (average 40%), implies its dual role in this organism.
