5T2K
Geobacillus stearothermophilus HemQ with Manganese-Coproporphyrin III
Summary for 5T2K
Entry DOI | 10.2210/pdb5t2k/pdb |
Descriptor | Putative heme-dependent peroxidase GT50_08830, [3,3',3'',3'''-(3,8,13,17-tetramethylporphyrin-2,7,12,18-tetrayl-kappa~4~N~21~,N~22~,N~23~,N~24~)tetra(propanoato)(2-)]manganese (3 entities in total) |
Functional Keywords | hemq, coproporphyrin iii, decarboxylation, oxidoreductase |
Biological source | Geobacillus stearothermophilus 10 |
Total number of polymer chains | 5 |
Total formula weight | 147626.20 |
Authors | Gauss, G.H.,Celis, A.I.,Dubois, J.L.,Peters, J.W. (deposition date: 2016-08-23, release date: 2017-01-18, Last modification date: 2023-10-04) |
Primary citation | Celis, A.I.,Gauss, G.H.,Streit, B.R.,Shisler, K.,Moraski, G.C.,Rodgers, K.R.,Lukat-Rodgers, G.S.,Peters, J.W.,DuBois, J.L. Structure-Based Mechanism for Oxidative Decarboxylation Reactions Mediated by Amino Acids and Heme Propionates in Coproheme Decarboxylase (HemQ). J. Am. Chem. Soc., 139:1900-1911, 2017 Cited by PubMed Abstract: Coproheme decarboxylase catalyzes two sequential oxidative decarboxylations with HO as the oxidant, coproheme III as substrate and cofactor, and heme b as the product. Each reaction breaks a C-C bond and results in net loss of hydride, via steps that are not clear. Solution and solid-state structural characterization of the protein in complex with a substrate analog revealed a highly unconventional HO-activating distal environment with the reactive propionic acids (2 and 4) on the opposite side of the porphyrin plane. This suggested that, in contrast to direct C-H bond cleavage catalyzed by a high-valent iron intermediate, the coproheme oxidations must occur through mediating amino acid residues. A tyrosine that hydrogen bonds to propionate 2 in a position analogous to the substrate in ascorbate peroxidase is essential for both decarboxylations, while a lysine that salt bridges to propionate 4 is required solely for the second. A mechanism is proposed in which propionate 2 relays an oxidizing equivalent from a coproheme compound I intermediate to the reactive deprotonated tyrosine, forming Tyr. This residue then abstracts a net hydrogen atom (H) from propionate 2, followed by migration of the unpaired propionyl electron to the coproheme iron to yield the ferric harderoheme and CO products. A similar pathway is proposed for decarboxylation of propionate 4, but with a lysine residue as an essential proton shuttle. The proposed reaction suggests an extended relay of heme-mediated e/H transfers and a novel route for the conversion of carboxylic acids to alkenes. PubMed: 27936663DOI: 10.1021/jacs.6b11324 PDB entries with the same primary citation |
Experimental method | X-RAY DIFFRACTION (1.8 Å) |
Structure validation
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