title: Complex Formation between Two Biosynthetic Enzymes Modifies the Allosteric Regulatory Properties of Both: AN EXAMPLE OF MOLECULAR SYMBIOSIS.
abstract: Allostery, where remote ligand binding alters protein function, is essential for the control of metabolism. Here, we have identified a highly sophisticated allosteric response that allows complex control of the pathway for aromatic amino acid biosynthesis in the pathogen Mycobacterium tuberculosis. This response is mediated by an enzyme complex formed by two pathway enzymes: chorismate mutase (CM) and 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase (DAH7PS). Whereas both enzymes are active in isolation, the catalytic activity of both enzymes is enhanced, and in particular that of the much smaller CM is greatly enhanced (by 120-fold), by formation of a hetero-octameric complex between CM and DAH7PS. Moreover, on complex formation M. tuberculosis CM, which has no allosteric response on its own, acquires allosteric behavior to facilitate its own regulatory needs by directly appropriating and partly reconfiguring the allosteric machinery that provides a synergistic allosteric response in DAH7PS. Kinetic and analytical ultracentrifugation experiments demonstrate that allosteric binding of phenylalanine specifically promotes hetero-octameric complex dissociation, with concomitant reduction of CM activity. Together, DAH7PS and CM from M. tuberculosis provide exquisite control of aromatic amino acid biosynthesis, not only controlling flux into the start of the pathway, but also directing the pathway intermediate chorismate into either Phe/Tyr or Trp biosynthesis.
authors.affiliation: Maurice Wilkins Centre and Biomolecular Interaction Centre, Department of Chemistry, University of Canterbury, Christchurch 8140, New Zealand.
authors.forename: Nicola J
authors.initials: NJ
authors.lastname: Blackmore
authors.affiliation: Maurice Wilkins Centre and Biomolecular Interaction Centre, Department of Chemistry, University of Canterbury, Christchurch 8140, New Zealand.
authors.forename: Ali Reza
authors.initials: AR
authors.lastname: Nazmi
authors.affiliation: Maurice Wilkins Centre and Biomolecular Interaction Centre, Department of Chemistry, University of Canterbury, Christchurch 8140, New Zealand.
authors.forename: Richard D
authors.initials: RD
authors.lastname: Hutton
authors.affiliation: Maurice Wilkins Centre and Biomolecular Interaction Centre, Department of Chemistry, University of Canterbury, Christchurch 8140, New Zealand.
authors.forename: Melissa N
authors.initials: MN
authors.lastname: Webby
authors.affiliation: Maurice Wilkins Centre and School of Biological Sciences, University of Auckland, Auckland 1142, New Zealand.
authors.forename: Edward N
authors.initials: EN
authors.lastname: Baker
authors.affiliation: Institute of Fundamental Sciences, Massey University, Palmerston North 4442, New Zealand. Electronic address: G.B.Jameson@massey.ac.nz.
authors.forename: Geoffrey B
authors.initials: GB
authors.lastname: Jameson
authors.affiliation: Maurice Wilkins Centre and Biomolecular Interaction Centre, Department of Chemistry, University of Canterbury, Christchurch 8140, New Zealand. Electronic address: emily.parker@canterbury.ac.nz.
authors.forename: Emily J
authors.initials: EJ
authors.lastname: Parker
mesh_terms: D010723:3-Deoxy-7-Phosphoheptulonate Synthase / Q000737:chemistry / Q000378:metabolism*; D000494:Allosteric Regulation; D024322:Amino Acids, Aromatic / Q000378:metabolism*; D002826:Chorismate Mutase / Q000737:chemistry / Q000378:metabolism*; D018360:Crystallography, X-Ray; D006801:Humans; D009169:Mycobacterium tuberculosis / Q000737:chemistry / Q000201:enzymology* / Q000378:metabolism; D055503:Protein Multimerization; D014376:Tuberculosis / Q000382:microbiology*
chemical_list: D024322:Amino Acids, Aromatic; D010723:3-Deoxy-7-Phosphoheptulonate Synthase; D002826:Chorismate Mutase
keywords: 3-deoxy-d-arabino-heptulosonate 7-phosphate synthase; Mycobacterium tuberculosis; TB; allosteric regulation; chorismate mutase; enzyme catalysis; oligomer; protein complex; protein-protein interaction; shikimate