Characterization of a New Ribotoxin Gene (c-sar) from Aspergillus Clavatus

A new ribotoxin, c-sarcin, was isolated from a culture of Aspergillus clavatus. A full-length genomic DNA (c-sar) coding for c-sarcin was cloned and sequenced. The deduced amino acid sequence showed a high homology to restrictocin and alpha-sarcin. The native toxin as well as the recombinant protein hydrolysed ribosomes and naked RNA. The genomic structure of the c-sar gene had an intron located between the coding sequences for secretory signal peptide and the mature protein. The intron contained a stretch of 38 adenines. The intron sequence of c-sar was different from that of restrictocin but resembled that of alpha-sarcin. There was 34% identity between the intron of c-sarcin and alpha-sarcin, and this similarity was further increased to 83% if the stretch of polyadenine was omitted.