title: Substrate control in stereoselective lanthionine biosynthesis.
abstract: Enzymes are typically highly stereoselective catalysts that enforce a reactive conformation on their native substrates. We report here a rare example in which the substrate controls the stereoselectivity of an enzyme-catalysed Michael-type addition during the biosynthesis of lanthipeptides. These natural products contain thioether crosslinks formed by a cysteine attack on dehydrated Ser and Thr residues. We demonstrate that several lanthionine synthetases catalyse highly selective anti-additions in which the substrate (and not the enzyme) determines whether the addition occurs from the re or si face. A single point mutation in the peptide substrate completely inverted the stereochemical outcome of the enzymatic modification. Quantum mechanical calculations reproduced the experimentally observed selectivity and suggest that conformational restraints imposed by the amino-acid sequence on the transition states determine the face selectivity of the Michael-type cyclization.
authors.affiliation: Department of Chemistry and Howard Hughes Medical Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Weixin
authors.initials: W
authors.lastname: Tang
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, USA.
authors.forename: Gonzalo
authors.initials: G
authors.lastname: Jiménez-Osés
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California 90095-1569, USA.
authors.forename: K N
authors.initials: KN
authors.lastname: Houk
authors.affiliation: Department of Chemistry and Howard Hughes Medical Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Wilfred A
authors.initials: WA
authors.lastname: van der Donk
mesh_terms: D000409:Alanine / Q000031:analogs & derivatives* / Q000032:analysis / Q000096:biosynthesis / Q000737:chemistry; D000595:Amino Acid Sequence; D003500:Cyclization; D008401:Gas Chromatography-Mass Spectrometry; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D011789:Quantum Theory; D013237:Stereoisomerism; D013379:Substrate Specificity; D013440:Sulfides / Q000032:analysis / Q000737:chemistry; D013816:Thermodynamics
chemical_list: D013440:Sulfides; C001520:lanthionine; D000409:Alanine