6jql
From Proteopedia
Structure of PaaZ, a bifunctional enzyme
Structural highlights
Function[PAAZ_ECOLI] Catalyzes the hydrolytic ring cleavage of 2-oxepin-2(3H)-ylideneacetyl-CoA (oxepin-CoA) via the open-chain aldehyde intermediate to yield 3-oxo-5,6-dehydrosuberyl-CoA. The enzyme consists of a C-terminal (R)-specific enoyl-CoA hydratase domain (formerly MaoC) that cleaves the ring and produces the highly reactive 3-oxo-5,6-dehydrosuberyl-CoA semialdehyde and an N-terminal NADP-dependent aldehyde dehydrogenase domain that oxidizes the aldehyde to 3-oxo-5,6-dehydrosuberyl-CoA. Can also use crotonyl-CoA as substrate.[1] [2] [3] Publication Abstract from PubMedSubstrate channeling is a mechanism for the internal transfer of hydrophobic, unstable or toxic intermediates from the active site of one enzyme to another. Such transfer has previously been described to be mediated by a hydrophobic tunnel, the use of electrostatic highways or pivoting and by conformational changes. The enzyme PaaZ is used by many bacteria to degrade environmental pollutants. PaaZ is a bifunctional enzyme that catalyzes the ring opening of oxepin-CoA and converts it to 3-oxo-5,6-dehydrosuberyl-CoA. Here we report the structures of PaaZ determined by electron cryomicroscopy with and without bound ligands. The structures reveal that three domain-swapped dimers of the enzyme form a trilobed structure. A combination of small-angle X-ray scattering (SAXS), computational studies, mutagenesis and microbial growth experiments suggests that the key intermediate is transferred from one active site to the other by a mechanism of electrostatic pivoting of the CoA moiety, mediated by a set of conserved positively charged residues. Molecular basis for metabolite channeling in a ring opening enzyme of the phenylacetate degradation pathway.,Sathyanarayanan N, Cannone G, Gakhar L, Katagihallimath N, Sowdhamini R, Ramaswamy S, Vinothkumar KR Nat Commun. 2019 Sep 11;10(1):4127. doi: 10.1038/s41467-019-11931-1. PMID:31511507[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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