6SLB image
Entry Detail
PDB ID:
6SLB
Keywords:
Title:
Crystal structure of isomerase PaaG with trans-3,4-didehydroadipyl-CoA
Biological Source:
PDB Version:
Deposition Date:
2019-08-19
Release Date:
2019-12-11
Method Details:
Experimental Method:
Resolution:
1.88 Å
R-Value Free:
0.21
R-Value Work:
0.16
Space Group:
P 21 3
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:Enoyl-CoA hydratase/carnithine racemase
Chain IDs:A (auth: AAA)
Chain Length:257
Number of Molecules:1
Biological Source:Thermus thermophilus JL-18
Ligand Molecules
Primary Citation
Structural and Mechanistic Basis of an Oxepin-CoA Forming Isomerase in Bacterial Primary and Secondary Metabolism.
Acs Chem.Biol. 14 2876 2886 (2019)
PMID: 31689071 DOI: 10.1021/acschembio.9b00742

Abstact

Numerous aromatic compounds are aerobically degraded in bacteria via the central intermediate phenylacetic acid (paa). In one of the key steps of this widespread catabolic pathway, 1,2-epoxyphenylacetyl-CoA is converted by PaaG into the heterocyclic oxepin-CoA. PaaG thereby elegantly generates an α,β-unsaturated CoA ester that is predisposed to undergo β-oxidation subsequent to hydrolytic ring-cleavage. Moreover, oxepin-CoA serves as a precursor for secondary metabolites (e.g., tropodithietic acid) that act as antibiotics and quorum-sensing signals. Here we verify that PaaG adopts a second role in aromatic catabolism by converting cis-3,4-didehydroadipoyl-CoA into trans-2,3-didehydroadipoyl-CoA and corroborate a Δ3,Δ2-enoyl-CoA isomerase-like proton shuttling mechanism for both distinct substrates. Biochemical and structural investigations of PaaG reveal active site adaptations to the structurally different substrates and provide detailed insight into catalysis and control of stereospecificity. This work elucidates the mechanism of action of unusual isomerase PaaG and sheds new light on the ubiquitous enoyl-CoA isomerases of the crotonase superfamily.

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