Referencia

JACS; 2017 May 8; 139(20):6795-6798. DOI: 10.1021/jacs.7b01626 Portada JACS

Autores

Iván Acebrón, Kiran V. Mahasenan, Stefania de Benedetti, Mijoon Lee, Cecilia Artola Recolons, Dusan Hesek, Huan Wang, Juan Antonio Hermoso y Shahriar Mobashery

Resumen

The N-acetylglucosaminidase NagZ of Pseudomonas aeruginosa catalyzes the first cytoplasmic step in recycling of muropeptides, cell-wall-derived natural products. This reaction regulates gene expression for the β-lactam resistance enzyme, β-lactamase. The enzyme catalyzes hydrolysis of N-acetyl-β-d-glucosamine-(1→4)-1,6-anhydro-N-acetyl-β-d-muramyl-peptide (1) to N-acetyl-β-d-glucosamine (2) and 1,6-anhydro-N-acetyl-β-d-muramyl-peptide (3). The structural and functional aspects of catalysis by NagZ were investigated by a total of seven X-ray structures, three computational models based on the X-ray structures, molecular-dynamics simulations and mutagenesis. The structural insights came from the unbound state and complexes of NagZ with the substrate, products and a mimetic of the transient oxocarbenium species, which were prepared by synthesis. The mechanism involves a histidine as acid/base catalyst, which is unique for glycosidases. The turnover process utilizes covalent modification of D244, requiring two transition-state species and is regulated by coordination with a zinc ion. The analysis provides a seamless continuum for the catalytic cycle, incorporating large motions by four loops that surround the active site.

Descripción

Desvelado el mecanismo catalítico de NagZ, una enzima clave en la resistencia a antibióticos de Pseudomonas aeruginosa

NagZ de Pseudomonas aeruginosa cataliza el primer paso del reciclaje de los muropéptidos (fragmentos naturales de la pared bacteriana) en el citoplasma y regula la expresión de la -lactamasa, la enzima clave en la resistencia a antibióticos -lactámicos. Los aspectos estructurales y funcionales de la catálisis de NagZ se investigaron mediante un total de siete estructuras cristalinas, dinámica molecular y por mutagénesis dirigida. Las estructuras muestran cambios estructurales profundos requeridos para la activación y descubren al Zn como un regulador de su actividad. El trabajo proporciona una imagen de todos los pasos del ciclo catalítico de NagZ en este importante patógeno humano.

 

 

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REFERENCIA DEL GRUPO INVESTIGADOR

La investigación en el grupo de Juan A. Hermoso se centra en la caracterización estructural de los mecanismos de virulencia y patogénesis bacteriana y en el modo de superarlos. Nos hemos focalizado en la Biología Estructural de las proteínas de la superficie bacteriana involucradas en funciones clave, tales como unión del patógeno al hospedador humano, resistencia a antibióticos, división o los procesos de remodelado de la pared bacteriana, cruciales en el desarrollo de la enfermedad infecciosa (http://www.xtal.iqfr.csic.es/grupo/xjuan/). Iván Acebrón ha desarrollado este trabajo como postdoctoral en el grupo de J.A. Hermoso y se encuentra actualmente en el grupo de D. Lietha en el CNIO.X

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