title: The crystal structure of the Pseudomonas dacunhae aspartate-beta-decarboxylase dodecamer reveals an unknown oligomeric assembly for a pyridoxal-5'-phosphate-dependent enzyme.
abstract: The Pseudomonas dacunhael-aspartate-beta-decarboxylase (ABDC, aspartate 4-decarboxylase, aspartate 4-carboxylyase, E.C. 4.1.1.12) is a pyridoxal-5'-phosphate (PLP)-dependent enzyme that catalyzes the beta-decarboxylation of l-aspartate to produce l-alanine and CO(2). This catalytically versatile enzyme is known to form functional dodecamers at its optimal pH and is thought to work in conjunction with an l-Asp/l-Ala antiporter to establish a proton gradient across the membrane that can be used for ATP biosynthesis. We have solved the atomic structure of ABDC to 2.35 A resolution using single-wavelength anomalous dispersion phasing. The structure reveals that ABDC oligomerizes as a homododecamer in an unknown mode among PLP-dependent enzymes and has highest structural homology with members of the PLP-dependent aspartate aminotransferase subfamily. The structure shows that the ABDC active site is very similar to that of aspartate aminotransferase. However, an additional arginine side chain (Arg37) was observed flanking the re-side of the PLP ring in the ABDC active site. The mutagenesis results show that although Arg37 is not required for activity, it appears to be involved in the ABDC catalytic cycle.
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of Georgia, Athens, GA 30602, USA.
authors.forename: Santiago
authors.initials: S
authors.lastname: Lima
authors.forename: Bakthavatsalam
authors.initials: B
authors.lastname: Sundararaju
authors.forename: Christina
authors.initials: C
authors.lastname: Huang
authors.forename: Roman
authors.initials: R
authors.lastname: Khristoforov
authors.forename: Cory
authors.initials: C
authors.lastname: Momany
authors.forename: Robert S
authors.initials: RS
authors.lastname: Phillips
mesh_terms: D001219:Aspartate Aminotransferases / Q000737:chemistry; D002262:Carboxy-Lyases / Q000737:chemistry* / Q000378:metabolism; D002384:Catalysis; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D019281:Dimerization; D008958:Models, Molecular; D011487:Protein Conformation; D021122:Protein Subunits / Q000737:chemistry / Q000378:metabolism; D011549:Pseudomonas / Q000201:enzymology*; D011732:Pyridoxal Phosphate / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D013329:Structure-Activity Relationship; D013379:Substrate Specificity
chemical_list: D021122:Protein Subunits; D011994:Recombinant Proteins; D011732:Pyridoxal Phosphate; D001219:Aspartate Aminotransferases; D002262:Carboxy-Lyases; C019747:aspartate 4-decarboxylase