ABSTRACT
Cytochrome P450 CYP121 is essential for the viability of Mycobacterium tuberculosis. Studies in vitro show that it can use the cyclodipeptide cyclo(l-Tyr-l-Tyr) (cYY) as a substrate. We report an investigation of the substrate and reaction specificities of CYP121 involving analysis of the interaction between CYP121 and 14 cYY analogues with various modifications of the side chains or the diketopiperazine (DKP) ring. Spectral titration experiments show that CYP121 significantly bound only cyclodipeptides with a conserved DKP ring carrying two aryl side chains in l-configuration. CYP121 did not efficiently or selectively transform any of the cYY analogues tested, indicating a high specificity for cYY. The molecular determinants of this specificity were inferred from both crystal structures of CYP121-analog complexes solved at high resolution and solution NMR spectroscopy of the analogues. Bound cYY or its analogues all displayed a similar set of contacts with CYP121 residues Asn(85), Phe(168), and Trp(182). The propensity of the cYY tyrosyl to point toward Arg(386) was dependent on the presence of the DKP ring that limits the conformational freedom of the ligand. The correct positioning of the hydroxyl of this tyrosyl was essential for conversion of cYY. Thus, the specificity of CYP121 results from both a restricted binding specificity and a fine-tuned P450 substrate relationship. These results document the catalytic mechanism of CYP121 and improve our understanding of its function in vivo. This work contributes to progress toward the design of inhibitors of this essential protein of M. tuberculosis that could be used for antituberculosis therapy.
Subject(s)
Bacterial Proteins/chemistry , Cytochrome P-450 Enzyme System/chemistry , Dipeptides/chemistry , Mycobacterium tuberculosis/enzymology , Peptides, Cyclic/chemistry , Antitubercular Agents/chemistry , Bacterial Proteins/antagonists & inhibitors , Catalytic Domain , Crystallography, X-Ray , Cytochrome P-450 Enzyme Inhibitors , Enzyme Inhibitors/chemistry , Hydrogen Bonding , Kinetics , Models, Molecular , Nuclear Magnetic Resonance, Biomolecular , Protein Binding , Solutions , Substrate SpecificityABSTRACT
New Yb(OTf)(3)-pyridylalkylamine complexes have been employed as chiral Lewis acids in the enantioselective Friedel-Crafts alkylation of indole derivatives with trifluoropyruvates. The influence of the substituents as well as the configuration of the ligands have been studied and allowed us to reach enantiomeric excesses up to 83%.
ABSTRACT
A useful synthesis of rare 1,2-disubstituted ferrocenylalkyl amines with (S(Fc),S) configuration has been achieved in a sequential one-pot methodology from (S)-p-tolylsulfinylferrocene.
Subject(s)
Amines/chemical synthesis , Ferrous Compounds/chemical synthesis , Amines/chemistry , Crystallography, X-Ray , Indicators and Reagents , Ligands , Models, Molecular , Molecular Conformation , StereoisomerismABSTRACT
(S)-tert-Butylsulfinylferrocene was submitted to ortho-metalation, and the corresponding lithium derivative was trapped by alkyl or aryl imines bearing various electron-withdrawing groups on the nitrogen atom (Ts, Dpp, Boc). New aminosulfoxides were obtained with complete diastereocontrol when Dpp or Boc groups were used. The absolute configuration (SS,SFc,S) has been determined by single-crystal X-ray analysis and chemical correlation. An unusual pseudocyclic boatlike transition state has been proposed to explain the stereochemical course of this reaction.
