Document Detail

A catalytic di-heme bis-Fe(IV) intermediate, alternative to an Fe(IV)=O porphyrin radical.
MedLine Citation:
PMID:  18562294     Owner:  NLM     Status:  MEDLINE    
High-valent iron species are powerful oxidizing agents in chemical and biological catalysis. The best characterized form of an Fe(V) equivalent described in biological systems is the combination of a b-type heme with Fe(IV)=O and a porphyrin or amino acid cation radical (termed Compound I). This work describes an alternative natural mechanism to store two oxidizing equivalents above the ferric state for biological oxidation reactions. MauG is an enzyme that utilizes two covalently bound c-type hemes to catalyze the biosynthesis of the protein-derived cofactor tryptophan tryptophylquinone. Its natural substrate is a monohydroxylated tryptophan residue present in a 119-kDa precursor protein. An EPR-silent di-heme reaction intermediate of MauG was trapped. Mössbauer spectroscopy revealed the presence of two distinct Fe(IV) species. One is consistent with an Fe(IV)=O (ferryl) species (delta = 0.06 mm/s, DeltaE(Q) = 1.70 mm/s). The other is assigned to an Fe(IV) heme species with two axial ligands from protein (delta = 0.17 mm/s, DeltaE(Q) = 2.54 mm/s), which has never before been described in nature. This bis-Fe(IV) intermediate is remarkably stable but readily reacts with its native substrate. These findings broaden our views of how proteins can stabilize a highly reactive oxidizing species and the scope of enzyme-catalyzed posttranslational modifications.
Xianghui Li; Rong Fu; Sheeyong Lee; Carsten Krebs; Victor L Davidson; Aimin Liu
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't     Date:  2008-06-18
Journal Detail:
Title:  Proceedings of the National Academy of Sciences of the United States of America     Volume:  105     ISSN:  1091-6490     ISO Abbreviation:  Proc. Natl. Acad. Sci. U.S.A.     Publication Date:  2008 Jun 
Date Detail:
Created Date:  2008-06-25     Completed Date:  2008-08-19     Revised Date:  2013-06-05    
Medline Journal Info:
Nlm Unique ID:  7505876     Medline TA:  Proc Natl Acad Sci U S A     Country:  United States    
Other Details:
Languages:  eng     Pagination:  8597-600     Citation Subset:  IM    
Department of Biochemistry, University of Mississippi Medical Center, 2500 North State Street, Jackson, MS 39216, USA.
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MeSH Terms
Bacterial Proteins / metabolism
Free Radicals / chemistry,  metabolism
Heme / chemistry*,  metabolism
Hemeproteins / chemistry*,  metabolism
Indolequinones / chemistry
Iron / chemistry*,  metabolism
Paracoccus denitrificans
Protein Processing, Post-Translational
Spectroscopy, Mossbauer
Tryptophan / analogs & derivatives,  chemistry
Grant Support
Reg. No./Substance:
0/Bacterial Proteins; 0/Free Radicals; 0/Hemeproteins; 0/Indolequinones; 134645-25-3/tryptophan tryptophylquinone; 14875-96-8/Heme; 73-22-3/Tryptophan; 7439-89-6/Iron

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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