2inn

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spinqualitylabelsall models 2inn, resolution 2.700Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Structure of the Phenol Hydroxyalse-Regulatory Protein Complex

Overview

Phenol hydroxylase (PH) belongs to a family of bacterial multicomponent, monooxygenases (BMMs) with carboxylate-bridged diiron active sites., Included are toluene/o-xylene (ToMO) and soluble methane (sMMO), monooxygenase. PH hydroxylates aromatic compounds, but unlike sMMO, it, cannot oxidize alkanes despite having a similar dinuclear iron active, site. Important for activity is formation of a complex between the, hydroxylase and a regulatory protein component. To address how structural, features of BMM hydroxylases and their component complexes may facilitate, the catalytic mechanism and choice of substrate, we determined X-ray, structures of native and SeMet forms of the PH hydroxylase (PHH) in, complex with its regulatory protein (PHM) to 2.3 A resolution. PHM binds, in a canyon on one side of the (alphabetagamma)2 PHH dimer, contacting, alpha-subunit helices A, E, and F approximately 12 A above the diiron, core. The structure of the dinuclear iron center in PHH resembles that of, mixed-valent MMOH, suggesting an Fe(II)Fe(III) oxidation state. Helix E, which comprises part of the iron-coordinating four-helix bundle, has more, pi-helical character than analogous E helices in MMOH and ToMOH lacking a, bound regulatory protein. Consequently, conserved active site Thr and Asn, residues translocate to the protein surface, and an approximately 6 A pore, opens through the four-helix bundle. Of likely functional significance is, a specific hydrogen bond formed between this Asn residue and a conserved, Ser side chain on PHM. The PHM protein covers a putative docking site on, PHH for the PH reductase, which transfers electrons to the PHH diiron, center prior to O2 activation, suggesting that the regulatory component, may function to block undesired reduction of oxygenated intermediates, during the catalytic cycle. A series of hydrophobic cavities through the, PHH alpha-subunit, analogous to those in MMOH, may facilitate movement of, the substrate to and/or product from the active site pocket. Comparisons, between the ToMOH and PHH structures provide insights into their substrate, regiospecificities.

About this Structure

2INN is a Protein complex structure of sequences from Pseudomonas stutzeri with , and as ligands. Full crystallographic information is available from OCA.

Reference

X-ray Structure of a Hydroxylase-Regulatory Protein Complex from a Hydrocarbon-Oxidizing Multicomponent Monooxygenase, Pseudomonas sp. OX1 Phenol Hydroxylase(,)., Sazinsky MH, Dunten PW, McCormick MS, Didonato A, Lippard SJ, Biochemistry. 2006 Dec 26;45(51):15392-15404. Epub 2006 Dec 2. PMID:17176061

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