title: Tryptophan synthase: the workings of a channeling nanomachine.
abstract: Substrate channeling between enzymes has an important role in cellular metabolism by compartmentalizing cytoplasmic synthetic processes. The bacterial tryptophan synthases are multienzyme nanomachines that catalyze the last two steps in L-tryptophan biosynthesis. The common metabolite indole is transferred from one enzyme to the other in each alphabeta-dimeric unit of the alpha2beta2 complex via an interconnecting 25-A-long tunnel. Recent solution studies of the Salmonella typhimurium alpha2beta2 complex coupled with X-ray crystal-structure determinations of complexes with substrates, intermediates and substrate analogs have driven important breakthroughs concerning the identification of the linkages between the bi-enzyme complex structure, catalysis at the alpha- and beta-active sites, and the allosteric regulation of substrate channeling.
authors.affiliation: Department of Biochemistry, University of California, Riverside, CA 92521, USA.
authors.forename: Michael F
authors.initials: MF
authors.lastname: Dunn
authors.forename: Dimitri
authors.initials: D
authors.lastname: Niks
authors.forename: Huu
authors.initials: H
authors.lastname: Ngo
authors.forename: Thomas R M
authors.initials: TR
authors.lastname: Barends
authors.forename: Ilme
authors.initials: I
authors.lastname: Schlichting
mesh_terms: D000494:Allosteric Regulation / Q000502:physiology; D001426:Bacterial Proteins / Q000737:chemistry* / Q000378:metabolism; D002384:Catalysis; D007211:Indoles / Q000737:chemistry / Q000378:metabolism; D020836:Protein Structure, Quaternary / Q000502:physiology; D012486:Salmonella typhimurium / Q000201:enzymology*; D014364:Tryptophan / Q000096:biosynthesis / Q000737:chemistry; D014367:Tryptophan Synthase / Q000737:chemistry* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D007211:Indoles; C030374:indole; D014364:Tryptophan; D014367:Tryptophan Synthase