The in vitro insertion of monoamine oxidase B into mitochondrial outer membranes

Abstract

Bovine monoamine oxidase (MAO) B has been synthesized in vitro using a reticulocyte lysate translation system directed by bovine liver poly(A)+ RNA. The newly synthesized enzyme apparently lacks a cleavable N‐terminal extension, but MAO B is readily incorporated into mitochondria or isolated mitochondrial outer membranes prepared from rat liver. ATP is not required for the binding of the newly synthesized enzyme to the outer membranes, but is necessary for the insertion of MAO B into these membrane vesicles. The ATP is not required to generate a mitochondrial membrane potential as assembly occurs under conditions that preclude either the formation or the maintenance of the potential. MAO B will bind to but not become incorporated into outer membrane vesicles which have been treated with trypsin, suggesting that the insertion of MAO B also depends on protein factors present on the outer membranes.

Geranylgeraniol oxidase activity involved in oxidative formation of geranylgeranoic acid in human hepatoma cells

“…At present, we speculate that a putative GGOH-binding protein may sequester the substrate for an enzyme located in the proteinase K-resistant mitochondrial compartment. Finally, we tested GGOH oxidase activity of MAO-B because: 1) farnesol, one-unit shorter isoprenol, has been identified as a selective inhibitor for MAO-B in tobacco smoke (9) and 2) MAO-B is localized to the inner side of the mitochondrial outer membrane and is known to be proteinase K-resistant (24,27). The present data met our expectations (Fig.…”

“…Most mammalian enzymes are susceptible to proteinase K digestion and lose their activity after the treatment, because proteinase K is a broadspectrum serine protease. But some enzymes incorporated into the mitochondrial compartment are known to be proteinase K-resistant (6,27). Indeed, GGOH oxidase activity was localized mainly to the mitochondrial fraction, explaining why GGOH oxidase activity in the cell lysates was resistant to proteinase K treatment.…”

“…Human MAO-B, localized to mitochondrial outer membrane, is known to be a proteinase K-resistant enzyme (27). Moreover, farnesol, C15 isoprenol depleted one isoprene unit from GGOH, was identified as a MAO-B selective inhibitor present in cigarette smoke extracts (9).…”

Mitochondrial morphological and functional defects in yeast caused by yme1 are suppressed by mutation of a 26S protease subunit homologue.

“…There is only limited evidence to support this hypothesis. For instance, ubiquitination may be associated with insertion of proteins into the mitochondrial outer membrane (Zhaung and McCauley, 1989;Magnani et al, 1991). A role for ubiquitination of proteins in organelle formation has been proposed based upon the observation that PAS2 in S. cerevisiae, a gene necessary for peroxisome biogenesis and proliferation, encodes a member of the ubiquitin-conjugating protein family (Wiebel and Kunau, 1992).…”

Immunocytochemical localization of monoamine oxidase type B in rat liver

“…The targeting signal is present within its carboxy-terminal 29 amino acid residues (Mitoma and Ito, 1992). It inserts into the membrane by ubiquitin (a 76-amino acid polypeptide), with energy provided by ATP (Zhaung and McCauley, 1989).…”