Structural insights into nucleotide and protein sequence of Ageritin: a novel prototype of fungal ribotoxin

Here, we report the amino acid sequence of Ageritin, the first ribotoxin-like protein from basidiomycetes (Agrocybe aegerita). This protein consists of 135 amino acid residues with a theoretical molecular mass of 14,801.80 Da (experimental mass 14,802.84 Da, [M + H+](+)). Unlike both the classic ribotoxins and homologous RNases T1 family from ascomycetes, Ageritin has a single free cysteinyl residue and does not show homology with known RNases endowed with the specific enzymatic activity on the universally conserved Sarcin Ricin Loop. On the other hand, our 3D homology study shows that Ageritin has a structural core consisting of an antiparallel beta-sheet and an adjacent long alpha-helix, typical of ribotoxins and RNase T1 family, although the sheet has an orthogonal arrangement with respect to them. Thus, Ageritin is the first prototype of novel ribotoxin-like protein family from fungi.