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Issue:
Volume 54, issue 6

Title: ANALYSIS OF UBIQUITIN-DEPENDENT INCREASE IN MONOAMINE OXIDASE SENSITIVITY TO PROTEOLYSIS AND SPECIFIC INHIBITION

Authors: O.A.Buneeva¹, M.V.Medvedeva², A.E.Medvedev¹

Address:

¹ Institute of Biomedical Chemistry, Russian Academy of Medical Sciences, 10 Pogodinskaya street, Moscow, 119121 Russia; fax: (499) 2450857; e-mail: olga.buneeva@ibmc.msk.ru;

² School of Biology, Moscow State University, Moscow, Russia.

 Abstract:

Insertion of exogenous ubiquitin into rat brain mitochondria in the presence of ATP and the ATP-regenerating system (creatine phosphate/creatine phosphokinase) is accompanied by the increase in: i) sensitivity of mitochondrial monoamine oxidases A and B to proteolytic inactivation (by trypsin and papain, respectively); ii) inhibition by mechanism based inhibitor, pargyline; iii) in [³H]-pargyline  insertion into mitochondria (+48 ± 11%, p<0.01). There was almost fivefold increase in [³H]-pargyline incorporation into the fraction obtained by immunoprecipitation of mitochondrial proteins with anti-ubiquitin antiserum and protein A Sepharose. This suggests that MAO is a potential substrate for  ubiquitination in vitro. However, the content of the tritium label in this fraction was less than 0.1% and not more than 0.25% of total radioactivity of [³H]pargyline bound to control and ATP-ubiquitin treated mitochondria, respectively. Insertion of ubiquitin into mitochondria did not influence molecular masses of [³H]-pargyline labeled proteins (MAO A and B). These results suggest that direct ubiquitination of MAO insignificantly contributes to marked changes in sensitivity of MAO A and MAO B to proteolysis and      specific inhibition found under these experimental conditions. It is possible that more complex processes are involved into realization of these effects during ATP-dependent ubiquitin incorporation into mitochondria.

Key words: monoamine oxidase, ubiquitin, proteolytic degradation, rat brain mitochondria, pargyline.

Биомедицинская химия, 2008 том 54, вып. 6, с. 720-726.

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