Characterization of a natural larger form of the antifungal protein (AFP) from Aspergillus giganteus.
Two major proteins, alpha-sarcin and an antifungal polypeptide (AFP), are secreted by the mould Aspergillus giganteus MDH 18894 when it is cultured for 70-80 h. A third major protein is also found in the extracellular medium at 48-60 h, but it disappears as the culture proceeds. This protein has been isolated and characterized in terms of apparent molecular mass, electrophoretic and chromatographic behaviour, NH2-terminal primary structure, amino acid content, spectroscopical features, reactivity against anti-AFP antibodies, and antifungal activity. Based on the obtained results it would be an extracellular inactive precursor form of AFP, designated as the large form of AFP (lf-AFP). Its amino acid composition is identical to that of AFP but containing six extra residues. NH2-terminal sequence analysis of the first eight amino acid residues of this polypeptide revealed that the extra residues can be perfectly accommodated within the DNA-deduced sequence of the precursor form of AFP. Its alignment with precursor sequences of different proteins, secreted by a variety of Aspergillus spp., reveals the existence of a common tetrapeptide at the carboxy-terminal end of their leader peptides. This sequence would be Ile/Leu-Xaa-Yaa-Arg, being mostly Xaa and Yaa an acid residue (Asp/Glu) and alanine, respectively. The presence of lf-AFP as an extracellular protein would be in perfect agreement with the existence of this tetrapeptide motif, that can be involved in the protein secretion mechanisms of filamentous fungi.
Martínez-Ruiz
A
A
Departamento de Bioquímica y Biología Molecular, Facultad de Quimíca, Universidad Complutense, Madrid, Spain.
Martínez del Pozo
A
A
Lacadena
J
J
Mancheño
J M
JM
Oñaderra
M
M
Gavilanes
J G
JG
D000595:Amino Acid Sequence; D000596:Amino Acids / Q000032:analysis; D001230:Aspergillus / Q000254:growth & development / Q000378:metabolism*; D002942:Circular Dichroism; D003470:Culture Media; D019281:Dimerization; D004591:Electrophoresis, Polyacrylamide Gel; D004722:Endoribonucleases / Q000302:isolation & purification; D005656:Fungal Proteins / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology; D005670:Fusarium / Q000187:drug effects; D008970:Molecular Weight; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D014242:Trichoderma / Q000187:drug effects
D000596:Amino Acids; D003470:Culture Media; D005656:Fungal Proteins; C097609:antifungal protein, Aspergillus; C014801:alpha-sarcin; D004722:Endoribonucleases