The carboxyl-terminal region of the yeast ATPase inhibitor is indispensable for the stability of the protein in mitochondria.
The role of the carboxyl-terminal region of the yeast mitochondrial ATPase inhibitor was investigated. Three progressive C-terminal deletion mutants of the inhibitor were constructed: (i) Ile58-->end; (ii) Ile51-->end; and (iii) Gln43-->end. The truncated inhibitor was detected in extracts of Ile58-->end mutant yeast cells. For the Ile51-->end mutant, the truncated inhibitor was only detected when the cells were grown on medium containing the membrane-permeable metal chelator, o-phenanthroline, which inhibits mitochondrial proteases. The most greatly truncated inhibitor protein, Gln43-->end, was never detected even in the cells grown in the presence of the metal chelator. The rates of ATP synthesis and hydrolysis in the mutant mitochondria containing the Ile51-->end inhibitor were similar to those in wild type control cells, while the Ile51-->end inhibitor protein was degraded in the cells unless they were incubated in the presence of the chelator. These results indicate that the carboxyl-terminal region of the ATPase inhibitor is not involved in the its inhibitory action on the F1Fo-ATPase, but is required for the stable conformation of the protein which is protected against degradation by proteases.
Ichikawa
N
N
Department of Food and Nutrition, Faculty of Human Life Science, Osaka City University, Sumiyoshi-ku, Osaka, 558-8585, Japan. ichikawa@life.osaka-cu.ac.jp.
Fukuda
M
M
Hashimoto
T
T
Tagawa
K
K
D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors*; D000595:Amino Acid Sequence; D001483:Base Sequence; D017931:DNA Primers; D006868:Hydrolysis; D008928:Mitochondria / Q000737:chemistry*; D008969:Molecular Sequence Data; D011506:Proteins / Q000737:chemistry*; D012441:Saccharomyces cerevisiae / Q000737:chemistry*; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D000097795:ATPase Inhibitory Protein
D000251:Adenosine Triphosphatases; D017931:DNA Primers; D011506:Proteins; D000097795:ATPase Inhibitory Protein