Yeast expression of the Tuber borchii fruiting body specific protein, TBF-1: identification of a noncanonical signal peptide.
The TBF-1 is an 11.9-kDa fruiting body specific protein of the Ascomycetes hypogeous fungus Tuber borchii Vittad. found in aqueous extract and the hyphal cell wall. The tbf-1 gene codes a 12-amino acid N-terminal stretch not present in mature protein. This sequence does not match with any homologous signal sequences stored in data banks. To investigate the role of the N-terminus in TBF-1 localization, cDNA was expressed in Saccharomyces cerevisiae under the control of the 3-phosphoglycerate kinase promoter. Like Tuber, yeast also produces and secretes TBF-1 and the foreign protein binds with the cell wall. A signalless mutant protein was constructed; this DeltaTBF-1 was expressed but not exported by yeast. The secretion of TBF-1 was also suppressed using the sec18(ts) yeast mutant strain grown at nonpermissive temperature as host. Thus we demonstrated that the N-terminal 12-amino acid stretch is a noncanonical signal peptide that leads the TBF-1 toward the classical secretory pathway in yeast.
Palma
Francesco
F
Istituto di Chimica Biologica Giorgio Fornaini, Università degli Studi di Urbino Carlo Bo, Urbino, Italy. fr.palma@uniurb.it
Cerigini
Emanuela
E
Stocchi
Vilberto
V
D001203:Ascomycota / Q000235:genetics*; D002473:Cell Wall / Q000737:chemistry; D003001:Cloning, Molecular; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism*; D015870:Gene Expression; D011485:Protein Binding; D021382:Protein Sorting Signals / Q000235:genetics*; D021381:Protein Transport; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics; D017384:Sequence Deletion
D005656:Fungal Proteins; D021382:Protein Sorting Signals; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; C117850:TBF-1 protein, Tuber borchii