The proteinase yscA‐inhibitor, I A 3 , gene Studies of cytoplasmic proteinase inhibitor deficiency on yeast physiology

• Published in: FEBS letters Vol. 283; no. 1; pp. 78 - 84
• Main Authors: Schu, Peter, Wolf, Dieter H.
• Format: Journal Article
• Language: English
• Published: 1991
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/0014-5793(91)80558-K

The gene of the proteinase yscA inhibitor I
A
3
,
, of the yeast
Saccharamyces cerevisiae
was isolated by oligonucleotide screening of a genomic DNA library and sequenced. The gene codes for a single protein of 68 amino acids. The structural
gene was deleted in vitro by oligonucleotide‐site‐directed mutagenesis. The mutated allele was introduced via homologous recombination into the genome of wild‐type yeast and into the genome of a yeast mutant, which lacks the second cytoplasmic proteinase‐inhibitor, I
B
2
. The deficiency of either or of both inhibitors has no effect on the cell viability under various physiological conditions. The inhibitor mutants, however, show an increase in the general in vivo protein degradation rate. The I
A
3
mutant has a 2–3‐fold increased protein degradation rate in the first 6 h after a shift from rich medium onto starvation‐medium, whereas the I
B
2
mutant shows a constantly increased degradation rate of 20–50% under the same conditions. The inhibitor double null mutant has the same protein degradation rate as the I
A
3
null mutant. These results suggest an in vivo interaction between the vacuolor endopeptidases and their cytoplasmic inhibitors.