3pvt
The Phenylacetyl-CoA monooxygenase PaaAC subcomplex with 3-hydroxybutanoyl-CoA
Structural highlights
FunctionPAAA_ECOLI Component of 1,2-phenylacetyl-CoA epoxidase multicomponent enzyme system which catalyzes the reduction of phenylacetyl-CoA (PA-CoA) to form 1,2-epoxyphenylacetyl-CoA. The subunit A is the catalytic subunit involved in the incorporation of one atom of molecular oxygen into phenylacetyl-CoA.[1] [2] [3] [4] Publication Abstract from PubMedThe utilization of phenylacetic acid (PA) in Escherichia coli occurs through a hybrid pathway that shows features of both aerobic and anaerobic metabolism. Oxygenation of the aromatic ring is performed by a multisubunit phenylacetyl-coenzyme A oxygenase complex that shares remote homology of two subunits to well-studied bacterial multicomponent mono-oxygenases (BMMs) and was postulated to form a new BMM subfamily. We expressed the subunits PaaA,B,C,D,E of the PA-CoA oxygenase and showed that PaaABC, PaaAC and PaaBC form stable sub-complexes that can be purified. In vitro reconstitution of the oxygenase subunits showed that each of the PaaA,B,C and E subunits are necessary for catalysis, while PaaD is not essential. We have determined the crystal structure of the PaaAC complex in a ligand-free form and with several CoA derivatives. We conclude that PaaAC forms a catalytic core with a monooxygenase fold with PaaA being the catalytic alpha subunit and PaaC - the structural beta subunit. PaaAC forms hetero-tetramers that are organized very differently from other known multisubunit monooxygenases and lacks their conservative network of hydrogen bonds between the di-iron center and protein surface, suggesting different association with the reductase and different mechanism of electron transport. The PaaA structure shows adaptation of the common access route to the active site for binding a CoA-bound substrate. The enzyme-substrate complex shows the orientation of the aromatic ring, which is poised for oxygenation at the ortho-position, in accordance with the expected chemistry. The PA-CoA oxygenase complex serves as a paradigm for the new subfamily multicomponent monooxygenases comprising several hundreds of homologs. Structural and functional studies of the Escherichia coli phenylacetyl-coa monooxygenase complex.,Grishin AM, Ajamian E, Tao L, Zhang L, Menard R, Cygler M J Biol Chem. 2011 Jan 19. PMID:21247899[5] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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