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Evidence that the catalytic mechanism of heme a synthase involves the formation of a carbocation stabilized by a conserved glutamate.
Rivett, Elise D; Addis, Hannah G; Dietz, Jonathan V; Carroll-Deaton, Jayda A; Gupta, Shipra; Foreman, Koji L; Dang, Minh Anh; Fox, Jennifer L; Khalimonchuk, Oleh; Hegg, Eric L.
Afiliación
  • Rivett ED; Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, MI, 48824, USA.
  • Addis HG; Department of Chemistry and Biochemistry, College of Charleston, Charleston, SC, 29424, USA.
  • Dietz JV; Department of Biochemistry, University of Nebraska, Lincoln, NE, 68588, USA.
  • Carroll-Deaton JA; Department of Chemistry and Biochemistry, College of Charleston, Charleston, SC, 29424, USA.
  • Gupta S; Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, MI, 48824, USA.
  • Foreman KL; Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, MI, 48824, USA.
  • Dang MA; Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, MI, 48824, USA.
  • Fox JL; Department of Chemistry and Biochemistry, College of Charleston, Charleston, SC, 29424, USA. Electronic address: foxjl@cofc.edu.
  • Khalimonchuk O; Department of Biochemistry, University of Nebraska, Lincoln, NE, 68588, USA; Nebraska Redox Biology Center, University of Nebraska, Lincoln, NE, 68588, USA; Fred & Pamela Buffett Cancer Center, Omaha, NE, 68198, USA. Electronic address: okhalimonchuk2@unl.edu.
  • Hegg EL; Department of Biochemistry & Molecular Biology, Michigan State University, East Lansing, MI, 48824, USA. Electronic address: erichegg@msu.edu.
Arch Biochem Biophys ; 744: 109665, 2023 08.
Article en En | MEDLINE | ID: mdl-37348627
In eukaryotes and many aerobic prokaryotes, the final step of aerobic respiration is catalyzed by an aa3-type cytochrome c oxidase, which requires a modified heme cofactor, heme a. The conversion of heme b, the prototypical cellular heme, to heme o and ultimately to heme a requires two modifications, the latter of which is conversion of a methyl group to an aldehyde, catalyzed by heme a synthase (HAS). The N- and C-terminal halves of HAS share homology, and each half contains a heme-binding site. Previous reports indicate that the C-terminal site is occupied by a heme b cofactor. The N-terminal site may function as the substrate (heme o) binding site, although this has not been confirmed experimentally. Here, we assess the role of conserved residues from the N- and C-terminal heme-binding sites in HAS from prokaryotic (Shewanella oneidensis) and eukaryotic (Saccharomyces cerevisiae) species - SoHAS/CtaA and ScHAS/Cox15, respectively. A glutamate within the N-terminal site is found to be critical for activity in both types of HAS, consistent with the hypothesis that a carbocation forms transiently during catalysis. In contrast, the residue occupying the analogous C-terminal position is dispensable for enzyme activity. In SoHAS, the C-terminal heme ligands are critical for stability, while in ScHAS, substitutions in either heme-binding site have little effect on global structure. In both species, in vivo accumulation of heme o requires the presence of an inactive HAS variant, highlighting a potential regulatory role for HAS in heme o biosynthesis.
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Texto completo: 1 Colección: 01-internacional Base de datos: MEDLINE Asunto principal: Ácido Glutámico / Proteínas de Saccharomyces cerevisiae Idioma: En Revista: Arch Biochem Biophys Año: 2023 Tipo del documento: Article País de afiliación: Estados Unidos Pais de publicación: Estados Unidos
Texto completo
Añadir a Mi BVS
Imprimir
XML
PubMed Links
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Texto completo: 1 Colección: 01-internacional Base de datos: MEDLINE Asunto principal: Ácido Glutámico / Proteínas de Saccharomyces cerevisiae Idioma: En Revista: Arch Biochem Biophys Año: 2023 Tipo del documento: Article País de afiliación: Estados Unidos Pais de publicación: Estados Unidos