2bf2
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CRYSTAL STRUCTURE OF NATIVE TOLUENE-4-MONOOXYGENASE CATALYTIC EFFECTOR PROTEIN, T4MOD
OverviewOverview
Toluene 4-monooxygenase (T4MO) is a four-component complex that catalyzes, the regiospecific, NADH-dependent hydroxylation of toluene to yield, p-cresol. The catalytic effector (T4moD) of this complex is a 102-residue, protein devoid of metals or organic cofactors. It forms a complex with the, diiron hydroxylase component (T4moH) that influences both the kinetics and, regiospecificity of catalysis. Here, we report crystal structures for, native T4moD and two engineered variants with either four (DeltaN4-) or 10, (DeltaN10-) residues removed from the N-terminal at 2.1-, 1.7-, and 1.9-A, resolution, respectively. The crystal structures have C-alpha, root-mean-squared differences of less than 0.8 A for the central core, consisting of residues 11-98, showing that alterations of the N-terminal, have little influence on the folded core of the protein. The central core, has the same fold topology as observed in the NMR structures of T4moD, the, methane monooxygenase effector protein (MmoB) from two methanotrophs, and, the phenol hydroxylase effector protein (DmpM). However, the, root-mean-squared differences between comparable C-alpha positions in the, X-ray structures and the NMR structures vary from approximately 1.8 A to, greater than 6 A. The X-ray structures exhibit an estimated overall, coordinate error from 0.095 (0.094) A based on the R-value (R free) for, the highest resolution DeltaN4-T4moD structure to 0.211 (0.196) A for the, native T4moD structure. Catalytic studies of the DeltaN4-, DeltaN7-, and, DeltaN10- variants of T4moD show statistically insignificant changes in, k(cat), K(M), k(cat)/K(M), and K(I) relative to the native protein., Moreover, there was no significant change in the regiospecificity of, toluene oxidation with any of the T4moD variants. The relative, insensitivity to changes in the N-terminal region distinguishes T4moD from, the MmoB homologues, which each require the approximately 33 residue, N-terminal region for catalytic activity.
About this StructureAbout this Structure
2BF2 is a Single protein structure of sequence from Pseudomonas mendocina. Full crystallographic information is available from OCA.
ReferenceReference
Crystal structures and functional studies of T4moD, the toluene 4-monooxygenase catalytic effector protein., Lountos GT, Mitchell KH, Studts JM, Fox BG, Orville AM, Biochemistry. 2005 May 17;44(19):7131-42. PMID:15882052
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