Domain Architecture of Pyruvate Carboxylase, a Biotin-Dependent Multifunctional Enzyme

• Published in: Science (American Association for the Advancement of Science) Vol. 317; no. 5841; pp. 1076 - 1079
• Main Authors: Maurice, Martin St, Reinhardt, Laurie, Surinya, Kathy H, Attwood, Paul V, Wallace, John C, Cleland, W. Wallace, Rayment, Ivan
• Format: Journal Article
• Language: English
• Published: Washington, DC American Association for the Advancement of Science 24.08.2007; The American Association for the Advancement of Science
• Subjects: Active sites; Adenosine Triphosphate - analogs & derivatives; Adenosine Triphosphate - metabolism; Allosteric Regulation; Binding Sites; Biochemistry; Biological and medical sciences; Biotin - metabolism; Carbon; Carboxyl compounds; Catalysis; Catalytic Domain; Coenzyme A - metabolism; Crystalline structure; Crystallography, X-Ray; Dimerization; Dimers; Enzyme Activators - metabolism; Enzymes; Fundamental and applied biological sciences. Psychology; Metabolism; Metal ions; Models, Molecular; Molecular biophysics; Molecular structure; Monomers; Mutation; Protein Structure, Quaternary; Protein Structure, Secondary; Protein Structure, Tertiary; Pyruvate Carboxylase - chemistry; Pyruvate Carboxylase - genetics; Pyruvate Carboxylase - metabolism; Rhizobium etli - enzymology; Structure in molecular biology; Carbon-carbon ligases; Enzyme; Ligases; Vitamin; B-Vitamins; Biotin; Pyruvate carboxylase; Crystalline structure
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.1144504

Biotin-dependent multifunctional enzymes carry out metabolically important carboxyl group transfer reactions and are potential targets for the treatment of obesity and type 2 diabetes. These enzymes use a tethered biotin cofactor to carry an activated carboxyl group between distantly spaced active sites. The mechanism of this transfer has remained poorly understood. Here we report the complete structure of pyruvate carboxylase at 2.0 angstroms resolution, which shows its domain arrangement. The structure, when combined with mutagenic analysis, shows that intermediate transfer occurs between active sites on separate polypeptide chains. In addition, domain rearrangements associated with activator binding decrease the distance between active-site pairs, providing a mechanism for allosteric activation. This description provides insight into the function of biotin-dependent enzymes and presents a new paradigm for multifunctional enzyme catalysis.