The biosynthesis of a cytotoxic protein, alpha-sarcin, in a mold of Aspergillus giganteus. II. Maturation of precursor form of alpha-sarcin in vivo.
Since Aspergillus giganteus ribosomes are sensitive to their own product, alpha-sarcin, we studied how resistance of protein synthesizing machinery is conferred in the cells. Immunoblotting analysis of a cell-extract prepared from mycelia of alpha-sarcin-producing phase showed two anti-alpha-sarcin reactive proteins which have molecular weights of 18.5 KDa and 16.9 KDa. The former and the latter were identified as the precursor and the mature forms of alpha-sarcin, respectively. Electronmicroscopic observation examining the location in situ by labeling with protein A-gold suggested that alpha-sarcin-related proteins are exclusively localized in large and small vacuoles. The small vacuoles, distributed near cell wall, appear to be involved in maturation and in the secretion of the protein. The present results suggested that alpha-sarcin is synthesized in an inactive precursor form and segregated in the membrane compartment through the synthesis and the maturation of alpha-sarcin in the cells.
Endo
Y
Y
Department of Biochemistry, Yamanashi Medical College, Japan.
Oka
T
T
Yokota
S
S
Tsurugi
K
K
Natori
Y
Y
D001230:Aspergillus / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D004722:Endoribonucleases; D005656:Fungal Proteins / Q000096:biosynthesis* / Q000235:genetics; D016253:Microscopy, Immunoelectron; D008970:Molecular Weight; D011498:Protein Precursors / Q000096:biosynthesis; D011499:Protein Processing, Post-Translational; D012331:RNA, Fungal / Q000235:genetics; D012335:RNA, Ribosomal / Q000235:genetics
D005656:Fungal Proteins; D011498:Protein Precursors; D012331:RNA, Fungal; D012335:RNA, Ribosomal; C065096:RNA, ribosomal, 26S; C014801:alpha-sarcin; D004722:Endoribonucleases