The insecticidal protein hirsutellin A from the mite fungal pathogen Hirsutella thompsonii is a ribotoxin.
The mite fungal pathogen Hirsutella thompsonii produces a single polypeptide chain, insecticidal protein named hirsutellin A (HtA) that is composed of 130 amino acid residues. This protein has been purified from its natural source and produced as a recombinant protein in Escherichia coli. Spectroscopic analysis has determined that the two protein forms are indistinguishable. HtA specifically inactivates ribosomes and produces the alpha-fragment characteristic of ribotoxin activity on rRNA. Behaving as a cyclizing ribonuclease, HtA specifically cleaves oligonucleotides that mimick the sarcin/ricin loop of the ribosome, as well as selected polynucleotides and dinucleosides. HtA interacts with phospholipid membranes as do other ribotoxins. As a consequence of its ribonuclease activity and its ability to interact with cell membranes, HtA exhibits cytotoxic activity on human tumor cells. On the basis of these results, HtA is considered to be a member of the ribotoxin group of proteins, although it is significantly smaller (130 aa) than all known ribotoxins that are composed of 149/150 amino acids. Ribotoxins are members of a larger family of fungal ribonucleases whose members of smaller size (100/110 aa) are not cytotoxic. Thus, the characterization of the fungal ribotoxin HtA represents an important milestone in the study of the diversity and the function of fungal ribonucleases.
Herrero-Galán
Elías
E
Departamento de Bioquímica y Biología Molecular I, Universidad Complutense, 28040 Madrid, Spain.
Lacadena
Javier
J
Martínez del Pozo
Alvaro
A
Boucias
Drion G
DG
Olmo
Nieves
N
Oñaderra
Mercedes
M
Gavilanes
José G
JG
D000595:Amino Acid Sequence; D000818:Animals; D016923:Cell Death / Q000187:drug effects; D002942:Circular Dichroism; D003001:Cloning, Molecular; D004722:Endoribonucleases / Q000737:chemistry / Q000378:metabolism; D005656:Fungal Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D007306:Insecticides / Q000494:pharmacology*; D007700:Kinetics; D050356:Lipid Metabolism / Q000187:drug effects; D008925:Mites / Q000382:microbiology*; D008969:Molecular Sequence Data; D009711:Nucleotides / Q000378:metabolism; D010715:Phosphatidylglycerols / Q000378:metabolism; D014176:Protein Biosynthesis / Q000187:drug effects; D011489:Protein Denaturation; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D012270:Ribosomes / Q000187:drug effects*; D016415:Sequence Alignment; D013696:Temperature
D005656:Fungal Proteins; C121692:Hirsutellin A protein, Hirsutella thompsonii; D007306:Insecticides; D009711:Nucleotides; D010715:Phosphatidylglycerols; D011994:Recombinant Proteins; C014801:alpha-sarcin; D004722:Endoribonucleases