title: Heterolytic OO bond cleavage: Functional role of Glu113 during bis-Fe(IV) formation in MauG.
abstract: The diheme enzyme MauG utilizes H2O2to perform oxidative posttranslational modification on a protein substrate. A bis-Fe(IV) species of MauG was previously identified as a key intermediate in this reaction. Heterolytic cleavage of the OO bond of H2O2drives the formation of the bis-Fe(IV) intermediate. In this work, we tested a hypothesis that a glutamate residue, Glu113 in the distal pocket of the pentacoordinate heme of MauG, facilitates heterolytic OO bond cleavage, thereby leading to bis-Fe(IV) formation. This hypothesis was proposed based on sequence alignment and structural comparison with other H2O2-utilizing hemoenzymes, especially those from the diheme enzyme superfamily that MauG belongs to. Electron paramagnetic resonance (EPR) characterization of the reaction between MauG and H2O2revealed that mutation of Glu113 inhibited heterolytic OO bond cleavage, in agreement with our hypothesis. This result was further confirmed by the HPLC study in which an analog of H2O2, cumene hydroperoxide, was used to probe the pattern of OO bond cleavage. Together, our data suggest that Glu113 functions as an acid-base catalyst to assist heterolytic OO bond cleavage during the early stage of the catalytic reaction. This work advances our mechanistic understanding of the H2O2-activation process during bis-Fe(IV) formation in MauG.
authors.affiliation: Department of Chemistry, Georgia State University, Atlanta, GA 30303, United States.
authors.forename: Jiafeng
authors.initials: J
authors.lastname: Geng
authors.affiliation: Department of Chemistry, Georgia State University, Atlanta, GA 30303, United States.
authors.forename: Lu
authors.initials: L
authors.lastname: Huo
authors.affiliation: Department of Chemistry, Georgia State University, Atlanta, GA 30303, United States; Department of Chemistry, University of Texas at San Antonio, San Antonio, TX 78249, United States. Electronic address: Feradical@utsa.edu.
authors.forename: Aimin
authors.initials: A
authors.lastname: Liu
mesh_terms: D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics; D018698:Glutamic Acid / Q000737:chemistry / Q000235:genetics; D006420:Hemeproteins / Q000737:chemistry* / Q000235:genetics; D006861:Hydrogen Peroxide / Q000737:chemistry*; D058085:Iron Compounds / Q000737:chemistry*; D010088:Oxidoreductases / Q000737:chemistry* / Q000235:genetics; D010100:Oxygen / Q000737:chemistry*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D006420:Hemeproteins; D058085:Iron Compounds; D011994:Recombinant Proteins; D018698:Glutamic Acid; D006861:Hydrogen Peroxide; D010088:Oxidoreductases; D010100:Oxygen
keywords: Cofactor biogenesis; Diheme; Ferryl intermediate; Mixed-valence; Reactive oxygen species; Remote catalysis