Structure of human monoamine oxidase A at 2.2-Å resolution: The control of opening the entry for substrates/inhibitors

Abstract

The mitochondrial outer membrane-anchored monoamine oxidase (MAO) is a biochemically important flavoenzyme that catalyzes the deamination of biogenic and xenobiotic amines. Its two subtypes, MAOA and MAOB, are linked to several psychiatric disorders and therefore are interesting targets for drug design. To understand the relationship between structure and function of this enzyme, we extended our previous low-resolution rat MAOA structure to the high-resolution wild-type and G110A mutant human MAOA structures at 2.2 and 2.17 Å, respectively. The high-resolution MAOA structures are similar to those of rat MAOA and human MAOB, but different from the known structure of human MAOA [De Colibus L, et al. (2005) Proc Natl Acad Sci USA 102:12684 -12689], specifically regarding residues 108 -118 and 210 -216, which surround the substrate/inhibitor cavity. The results confirm that the inhibitor selectivity of MAOA and MAOB is caused by the structural differences arising from Ile-335 in MAOA vs. Tyr-326 in MAOB. The structures exhibit a C-terminal transmembrane helix with clear electron density, as is also seen in rat MAOA. Mutations on one residue of loop 108 -118, G110, which is far from the active center but close to the membrane surface, cause the solubilized enzyme to undergo a dramatic drop in activity, but have less effect when the enzyme is anchored in the membrane. These results suggest that the flexibility of loop 108 -118, facilitated by anchoring the enzyme into the membrane, is essential for controlling substrate access to the active site. We report on the observation of the structure-function relationship between a transmembrane helical anchor and an extra-membrane domain.single transmembrane helix ͉ transmembrane helical anchor ͉ harmine ͉ x-ray structure M onoamine oxidase (MAO) is an enzyme localized to the mitochondrial outer membrane and catalyzes the deamination of biogenic and xenobiotic amines, such as neuroactive serotonin, norepinephrine, and dopamine. MAO contains a flavin adenine dinucleotide (FAD) covalently bound to a cysteine residue by an 8␣-(S-cysteinyl)-riboflavin linkage (1). MAO plays a decisive role in some psychiatric and neurological disorders, including depression and Parkinson's disease. Because inhibition of MAO increases the level of neurotransmitters in the central nervous system, searching for the effective inhibitors represents one important approach to developing novel drugs to treat such illnesses. MAO has two subtypes, MAOA and MAOB, whose amino acid sequences are up to 70% identical, although each enzyme has unique substrate and inhibitor specificities (2): MAOA oxidizes serotonin, whereas MAOB does not; MAOA is selectively inhibited by clorgyline, whereas MAOB is highly inhibited by deprenyl. In addition, the oxidative deamination produces harmful hydrogen peroxide that may further generate free radicals (3). Development of selective and reversible MAO inhibitors is important not only from the standpoint of treating symptoms (i.e., by increasing the biological half-life of mo...

O2 Reactivity of Flavoproteins

“…/HOO Ϫ . This role has been assigned to a His in glucose oxidase (12,32) and to a Lys in monomeric sarcosine oxidase (36) and in monoamine oxidase (37,38). In DAAO, this would be implemented by the proposed H ϩ relay system.…”

20 ans après: a second mutation in MAOA identified by targeted high-throughput sequencing in a family with altered behavior and cognition

“…Interestingly, a full-length crystal structure of the human MAOA is available (Protein Data Bank 2Z5Y, from positions 12-524 out of 527 aa). 37 The analysis of the modeled 3D structure by the prediction program KD4v indicates that the missense affects an aminoacid in a beta sheet close to the FAD-binding pocket, and the bulky aromatic ring of phenylalanine is oriented toward the FAD-binding pocket (Figure 1e), which may explain the observed effect on enzymatic activity (see below). We also genotyped the VNTR located in the MAOA promoter and observed that the proband III-1 carries the 3R (three repeats) allele, associated with 'low expression' of MAOA, 13 which may thus potentiate the effect of the missense mutation on the level of MAOA activity.…”

Monoamine Oxidase Inhibitors—Revisiting a Therapeutic Principle

“…Its structure is closely related to pargyline which has a slight selectivity for MAO-B. The reason for this difference in selectivity can be explained by the 3-dimentional structure of the enzymes and caused by the structural differences arising from Ile-335 in MAO-A versus Tyr-326 in MAO constraining the access to the active centre and limiting the access of clorgiline (Son, 2008). Clorgiline was never marketed but used as tool in scientific research and further search for selective MAO-A inhibitors finally cumulate in the discovery of reversible and selective inhibitors of MAO-A also known as RIMAs.…”