Tohoku J. Exp. Med., 2001, 195 (3)

Activation of Mitochondrial ATP-Dependent Proteaseby Peptides and Proteins

SHOJI WATABE, MASAYUKI HARA,¹ MISA YAMAMOTO, MINORU YOSHIDA,²
YOSHIMI YAMAMOTO³ and SUSUMU Y. TAKAHASHI³

Basic Laboratory Sciences, Faculty of Health Sciences, Yamaguchi University School of Medicine, Ube 755-8554,
¹Department of Anatomy and ²Department of Chemistry, St. Marianna University School of Medicine, Kawasaki 216-8511, and
³Department of Biochemistry and Radiation Biology, Faculty of Agriculture, Yamaguchi University, Yamaguchi 753-8515

We examined the effect of peptides or protein on the proteolytic and ATPase activities of mitochondrial ATP-dependent LON protease purified from bovine adrenal cortex. Peptides/proteins including angiotensin I which stimulated ATPase activity without hydrolysis of any peptide bonds stimulated proteolysis of ¹²⁵I-labeled substrates at low concentrations; whereas at high concentrations they competitively inhibited proteolysis, thus displaying a biphasic activity profile. All peptides and proteins thus examined stimulated degradation of ¹²⁵I-labeled substrates. When an ATP analog was substituted for ATP, only inhibition; i.e., no stimulation, of proteolysis by unlabeled peptides was observed. Without activator peptides, degradation of [¹²⁵I]peptides was higher in the presence of an ATP analog than that in the presence of ATP. ADP, a product of the ATPase reaction, inhibited the proteolytic activity in the absence of an activator peptide but not in its presence. From analogy to E. coli ATP-dependent protease La (LON), we suggest that the activator peptides stimulated the proteolysis by releasing enzyme-bound ADP.

Keywords —— ATP-dependent protease; adrenal cortex; mitochondria; activation; protein degradation

© 2001 Tohoku University Medical Press

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Tohoku J. Exp. Med., 2001, 195, 153-161

Address for reprints: Shoji Watabe, Basic Laboratory Sciences, Faculty of Health Sciences, Yamaguchi University School of Medicine, 1-1-1 Minami-Kogushi, Ube 755-8554, Japan.

e-mail: shwatabe@yamaguchi-u.ac.jp