Ribotoxin genes in isolates of Aspergillus section Clavati.
Ribotoxins are ribosome inactivator proteins with high specificity against the sarcin/ricin domain of the 28S ribosomal RNA. We examined the presence of ribotoxin genes in isolates of species recently assigned to Aspergillus section Clavati using specific primer pairs. All species assigned to this section have been found to carry ribotoxin genes. Phylogenetic analysis of the sequences of the amplified gene fragments allowed us to classify the genes to different groups including the alpha-sarcin, gigantin, c-sarcin and mitogillin/restrictocin families. Two species, A. longivesica and N. acanthosporus produced ribotoxins which were only distantly related to gigantins and c-sarcins, respectively. Comparison of the protein sequences of the genes to known ribotoxin sequences revealed that all of them carry the presumed catalytic residues of ribotoxins, the cystein residues, and also the two Trp residues of alpha-sarcin conserved in all ribotoxins known so far. These data indicate that these genes probably encode active ribotoxins. Further studies are in progress to examine the secretion and activities of these new ribotoxins.
Varga
János
J
CBS Fungal Biodiversity Centre, Uppsalalaan 8, Utrecht, The Netherlands. j.varga@cbs.knaw.nl
Samson
Robert A
RA
D000595:Amino Acid Sequence; D001230:Aspergillus / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics*; D005800:Genes, Fungal; D008969:Molecular Sequence Data; D010802:Phylogeny; D054788:Ribosome Inactivating Proteins / Q000737:chemistry / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity
D005656:Fungal Proteins; D054788:Ribosome Inactivating Proteins