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dc.contributor.authorStreit, Bennett R.
dc.contributor.authorCelis Luna, Arianna I.
dc.contributor.authorMoraski, Garrett C.
dc.contributor.authorShisler, Krista A.
dc.contributor.authorShepard, Eric M.
dc.contributor.authorRodgers, Kenton R.
dc.contributor.authorLukat-Rodgers, Gudrun S.
dc.contributor.authorDuBois, Jennifer L.
dc.identifier.citationStreit, Bennett R. , Arianna Celis Luna, Garrett C. Moraski, Krista Shisler, Eric M. Shepard, Kenton R. Rodgers, Gudrun S. Lukat-Rodgers, and Jennifer L. DuBois. "Decarboxylation involving a ferryl, propionate, and a tyrosyl group in a radical relay yields heme b." The Journal of Biological Chemistry (February 2018). DOI: 10.1074/jbc.RA117.000830.en_US
dc.description.abstractThe H2O2-dependent oxidative decarboxylation of coproheme III is the final step in the biosynthesis of heme<em> b</em> in many microbes. However, the coproheme decarboxylase reaction mechanism is unclear. The structure of the decarboxylase in complex with coproheme III suggested that the substrate iron, reactive propionates, and an active-site tyrosine convey a net 2e-/2H+ from each propionate to an activated form of H2O2 Time-resolved EPR spectroscopy revealed that Tyr-145 forms a radical species within 30 sec of the reaction of the enzyme-coproheme complex with H2O2 This radical disappeared over the next 270 sec, consistent with a catalytic intermediate. Use of the harderoheme III intermediate as substrate or substitutions of redox-active side chains (W198F, W157F, or Y113S) did not strongly affect the appearance or intensity of the radical spectrum measured 30 sec after initiating the reaction with H2O2, nor did it change the ~270 sec required for the radical signal to recede to ≤ 10% of its initial intensity. These results suggested Tyr-145 as the site of a catalytic radical involved in decarboxylating both propionates. Tyr-145 was accompanied by partial loss of the initially present Fe(III) EPR signal intensity, consistent with the possible formation of Fe(IV)=O. Site-specifically deuterated coproheme gave rise to a kinetic isotope effect of ~2 on the decarboxylation rate constant, indicating that cleavage of the propionate Cbeta-H bond was partly rate limiting. The inferred mechanism requires two consecutive hydrogen atom transfers, first from Tyr-145 to the substrate Fe/H2O2 intermediate and then from the propionate Cbeta-H to Tyr-145.en_US
dc.description.sponsorshipNIGMS, National Institutes of Health, Grants R01GM090260 (to J. L. D.) and R15GM114787 (to G. S. L.-R.)en_US
dc.rightsThis Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).en_US
dc.titleDecarboxylation involving a ferryl, propionate, and a tyrosyl group in a radical relay yields heme ben_US
mus.citation.journaltitleJournal of Biological Chemistryen_US
mus.identifier.categoryChemical & Material Sciencesen_US
mus.identifier.categoryLife Sciences & Earth Sciencesen_US
mus.relation.collegeCollege of Letters & Scienceen_US
mus.relation.departmentChemistry & Biochemistry.en_US
mus.relation.universityMontana State University - Bozemanen_US
mus.contributor.orcidMoraski, Garrett C.|0000-0002-6992-5584en_US

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