title: QM/MM study of the C-C coupling reaction mechanism of CYP121, an essential cytochrome p450 of Mycobacterium tuberculosis.
abstract: Among 20 p450s of Mycobacterium tuberculosis (Mt), CYP121 has received an outstanding interest, not only due to its essentiality for bacterial viability but also because it catalyzes an unusual carbon-carbon coupling reaction. Based on the structure of the substrate bound enzyme, several reaction mechanisms were proposed involving first Tyr radical formation, second Tyr radical formation, and C-C coupling. Key and unknown features, being the nature of the species that generate the first and second radicals, and the role played by the protein scaffold each step. In the present work we have used classical and quantum based computer simulation methods to study in detail its reaction mechanism. Our results show that substrate binding promotes formation of the initial oxy complex, Compound I is the responsible for first Tyr radical formation, and that the second Tyr radical is formed subsequently, through a PCET reaction, promoted by the presence of key residue Arg386. The final C-C coupling reaction possibly occurs in bulk solution, thus yielding the product in one oxygen reduction cycle. Our results thus contribute to a better comprehension of MtCYP121 reaction mechanism, with direct implications for inhibitor design, and also contribute to our general understanding of these type of enzymes.
authors.affiliation: Departamento de Quimica Biológica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Intendente Güiraldes, 2160, C1428EGA, Ciudad Autónoma de Buenos Aires, Argentina; Instituto de Química Física de los Materiales Medio Ambiente y Energia (INQUIMAE), UBA-CONICET, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Intendente Güiraldes, 2160, C1428EGA, Ciudad Autónoma de Buenos Aires, Argentina.
authors.forename: Victoria G
authors.initials: VG
authors.lastname: Dumas
authors.forename: Lucas A
authors.initials: LA
authors.lastname: Defelipe
authors.forename: Ariel A
authors.initials: AA
authors.lastname: Petruk
authors.forename: Adrian G
authors.initials: AG
authors.lastname: Turjanski
authors.forename: Marcelo A
authors.initials: MA
authors.lastname: Marti
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry*; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry*; D054659:Diketopiperazines / Q000737:chemistry; D005609:Free Radicals / Q000737:chemistry; D056004:Molecular Dynamics Simulation; D009169:Mycobacterium tuberculosis / Q000201:enzymology*; D016877:Oxidants / Q000737:chemistry; D010084:Oxidation-Reduction; D011485:Protein Binding; D011789:Quantum Theory; D012996:Solutions; D013816:Thermodynamics; D014443:Tyrosine / Q000737:chemistry
chemical_list: D001426:Bacterial Proteins; D054659:Diketopiperazines; D005609:Free Radicals; D016877:Oxidants; D012996:Solutions; C464825:cytochrome P-450 CYP121; C573447:mycocyclosin; C408694:tyrosine radical; D014443:Tyrosine; D003577:Cytochrome P-450 Enzyme System
keywords: CYP121; Mycobacterium tuberculosis; QM/MM; cyclo-di-tyrosine; cytochrome p450; electron transfer; molecular dynamics; reaction mechanism