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The available literature implicating human monoamine oxidase A (MAO A) in apoptotic processes reports levels of MAO A protein that do not corre-late with activity, suggesting that unknown mechanisms may be involved in the regulation of catalytic function. | ỊFEBS Journal Mutagenic probes of the role of Ser209 on the cavity shaping loop of human monoamine oxidase A Jin Wang1 Johnny Harris1 Darrell D. Mousseau2 and Dale E. Edmondson1 1 Departments of Biochemistry and Chemistry Emory University Atlanta GA USA 2 CellSignaling Laboratory Department of Psychiatry University of Saskatchewan Saskatoon Canada Keywords cavity-shaping loop membrane monoamine oxidase A mutagenesis phosphomimic Correspondence D. E. Edmondson Department of Biochemistry Emory University Atlanta GA 30322 USA Fax 1 404 727 2738 Tel 1 404 727 5972 E-mail deedmon@emory.edu Present address Departments of Biochemistry and Molecular Biology University of Florida Gainesville FL USA Received 6 May 2009 revised 17 June 2009 accepted 19 June 2009 doi 10.1111 j.1742-4658.2009.07162.x The available literature implicating human monoamine oxidase A MAO A in apoptotic processes reports levels of MAO A protein that do not correlate with activity suggesting that unknown mechanisms may be involved in the regulation of catalytic function. Bioinformatic analysis suggests Ser209 as a possible phosphorylation site that may be relevant to catalytic function because it is adjacent to a six-residue loop termed the cavity shaping loop from structural data. To probe the functional role of this site MAO A Ser209Ala and Ser209Glu mutants were created and investigated. In its membrane-bound form the MAO A Ser209Glu phosphorylation mimic exhibits catalytic and inhibitor binding properties similar to those of wildtype MAO A. Solubilization in detergent solution and purification of the Ser209Glu mutant results in considerable decreases in these functional parameters. By contrast the MAO A Ser209Ala mutant exhibits similar catalytic properties to those of wild-type enzyme when purified. Compared to purified wild-type and Ser209Ala MAO A proteins the Ser209Glu MAO A mutant shows significant differences in covalent flavin fluorescence yield CD spectra and thermal stability. These .
