Publications

• Solution structure of phenol hydroxylase protein component P2 determined by NMR spectroscopy.

  Qian H., Edlund U., Powlowski J., Shingler V., Sethson I.

  Phenol hydroxylase from Pseudomonas sp. CF600 is a member of a family of binuclear iron-center-containing multicomponent oxygenases, which catalyzes the conversion of phenol and some of its methyl-substituted derivatives to catechol. In addition to a reductase component which transfers electrons f ... >> More

  Phenol hydroxylase from Pseudomonas sp. CF600 is a member of a family of binuclear iron-center-containing multicomponent oxygenases, which catalyzes the conversion of phenol and some of its methyl-substituted derivatives to catechol. In addition to a reductase component which transfers electrons from NADH, optimal turnover of the hydroxylase requires P2, a protein containing 90 amino acids which is readily resolved from the other components. The three-dimensional solution structure of P2 has been solved by 3D heteronuclear NMR spectroscopy. On the basis of 1206 experimental constraints, including 1060 distance constraints obtained from NOEs, 70 phi dihedral angle constraints, 42 psi dihedral angle constraints, and 34 hydrogen bond constraints, a total of 12 converged structures were obtained. The atomic root mean square deviation for the 12 converged structure with respect to the mean coordinates is 2.48 A for the backbone atoms and 3.85 A for all the heavy atoms. This relatively large uncertainty can be ascribed to conformational flexibility and exchange. The molecular structure of P2 is composed of three helices, six antiparallel beta-strands, one beta-hairpin, and some less ordered regions. This is the first structure among the known multicomponent oxygenases. On the basis of the three-dimensional structure of P2, sequence comparisons with similar proteins from other multicomponent oxygenases suggested that all of these proteins may have a conserved structure in the core regions. << Less

  Biochemistry 36:495-504(1997) [PubMed] [EuropePMC]

• On the role of DmpK, an auxiliary protein associated with multicomponent phenol hydroxylase from Pseudomonas sp. strain CF600.

  Powlowski J., Sealy J., Shingler V., Cadieux E.

  DmpK from Pseudomonas sp. strain CF600 represents a group of proteins required by phenol-degrading bacteria that utilize a multicomponent iron-containing phenol hydroxylase. DmpK has been overexpressed in Escherichia coli and purified to homogeneity; it lacks redox cofactors and was found to stron ... >> More

  DmpK from Pseudomonas sp. strain CF600 represents a group of proteins required by phenol-degrading bacteria that utilize a multicomponent iron-containing phenol hydroxylase. DmpK has been overexpressed in Escherichia coli and purified to homogeneity; it lacks redox cofactors and was found to strongly inhibit phenol hydroxylase in vitro. Chemical cross-linking experiments established that DmpK binds to the two largest subunits of the oxygenase component of the hydroxylase; this may interfere with binding of the hydroxylase activator protein, DmpM, causing inhibition. Since expression of DmpK normally appears to be much lower than that of the components of the oxygenase, inhibition may not occur in vivo. Hence, the interaction between DmpK and the oxygenase manifested in the inhibition and cross-linking results prompted construction of E. coli strains in which the oxygenase component was expressed in the presence and absence of a low molar ratio of DmpK. Active oxygenase was detected only when expressed in the presence of DmpK. Furthermore, inactive oxygenase could be activated in vitro by adding ferrous iron, in a process that was dependent on the presence of DmpK. These results indicate that DmpK plays a role in assembly of the active form of the oxygenase component of phenol hydroxylase. << Less

  J. Biol. Chem. 272:945-951(1997) [PubMed] [EuropePMC]

• In vitro analysis of polypeptide requirements of multicomponent phenol hydroxylase from Pseudomonas sp. strain CF600.

  Powlowski J., Shingler V.

  An in vitro study of the multicomponent phenol hydroxylase from Pseudomonas sp. strain CF600 was performed. Phenol-stimulated oxygen uptake from crude extracts was strictly dependent on the addition of NAD(P)H and Fe2+ to assay mixtures. Five of six polypeptides required for growth on phenol were ... >> More

  An in vitro study of the multicomponent phenol hydroxylase from Pseudomonas sp. strain CF600 was performed. Phenol-stimulated oxygen uptake from crude extracts was strictly dependent on the addition of NAD(P)H and Fe2+ to assay mixtures. Five of six polypeptides required for growth on phenol were necessary for in vitro activity. One of the polypeptides was purified to homogeneity and found to be a flavin adenine dinucleotide containing iron-sulfur protein with significant sequence homology, at the amino terminus, to plant-type ferredoxins. This component, as in other oxygenase systems, probably functions to transfer electrons from NAD(P)H to the iron-requiring oxygenase component. Phenol hydroxylase from this organism is thus markedly different from bacterial flavoprotein monooxygenases commonly used for hydroxylation of other phenolic compounds, but bears a number of similarities to multicomponent oxygenase systems for unactivated compounds. << Less

  J. Bacteriol. 172:6834-6840(1990) [PubMed] [EuropePMC]

• Biochemical, Moessbauer, and EPR studies of the diiron cluster of phenol hydroxylase from Pseudomonas sp. strain CF 600.

  Cadieux E., Vrajmasu V., Achim C., Powlowski J., Muenck E.

  Phenol hydroxylase of Pseudomonas sp. strain CF600 comprises three components: DmpP is an FAD- and [2Fe-2S]-containing reductase; DmpM is a cofactorless activator protein; and DmpLNO is the oxygenase. Single turnover experiments established that DmpLNO contains the active site, but requires DmpM f ... >> More

  Phenol hydroxylase of Pseudomonas sp. strain CF600 comprises three components: DmpP is an FAD- and [2Fe-2S]-containing reductase; DmpM is a cofactorless activator protein; and DmpLNO is the oxygenase. Single turnover experiments established that DmpLNO contains the active site, but requires DmpM for efficient turnover: the steady-state turnover rate reaches a maximum at 1.5 DmpM:1 DmpLNO. Chemical cross-linking experiments showed that DmpM interacts with the large subunit of the DmpLNO oxygenase complex. Mössbauer studies revealed that the active site of the oxygenase can accommodate two types of diiron clusters, each of these cluster types having two equivalent sites. Cluster form I, representing typically around 85% of total Fe, has DeltaE(Q) = 1.73 mm/s and delta = 0.54 mm/s, while cluster II exhibits DeltaE(Q) = 0.79 mm/s and delta = 0.48 mm/s. Studies in strong applied magnetic fields suggest that the two iron sites of cluster I are bridged by an oxo group while sites in cluster II appear to be hydroxo-bridged. Reduction of the samples with dithionite yields the diferrous forms of the clusters. Air oxidation of the reduced samples leads to an increase of the cluster II fraction, accompanied by a corresponding decrease in catalytic activity. The reduced oxygenase samples exhibit at X-band an integer spin EPR signal centered, in parallel mode, at g = 16.6. Quantitative analysis showed that 19% of the clusters contribute to the EPR signal, suggesting that cluster II is the EPR-active species. Incubation with dithiothreitol (DTT) inactivated the oxygenase by a mechanism apparently involving H(2)O(2) generation. In addition, Mössbauer studies of DTT-inactivated enzyme showed that all ferric iron belonged to one diamagnetic diferric cluster with parameters that indicate that DTT coordinates to the cluster. << Less

  Biochemistry 41:10680-10691(2002) [PubMed] [EuropePMC]

• Complete nucleotide sequence and polypeptide analysis of multicomponent phenol hydroxylase from Pseudomonas sp. strain CF600.

  Nordlund I., Powlowski J., Shingler V.

  Pseudomonas sp. strain CF600 metabolizes phenol and some of its methylated derivatives via a plasmid-encoded phenol hydroxylase and meta-cleavage pathway. The genes encoding the multicomponent phenol hydroxylase of this strain are located within a 5.5-kb SacI-NruI fragment. We report the nucleotid ... >> More

  Pseudomonas sp. strain CF600 metabolizes phenol and some of its methylated derivatives via a plasmid-encoded phenol hydroxylase and meta-cleavage pathway. The genes encoding the multicomponent phenol hydroxylase of this strain are located within a 5.5-kb SacI-NruI fragment. We report the nucleotide sequence and the polypeptide products of this 5.5-kb region. A combination of deletion analysis, expression of subfragments in tac expression vectors, and identification of polypeptide products in maxicells was used to demonstrate that the polypeptides observed are produced from the six open reading frames identified in the sequence. Expression of phenol hydroxylase activity in a laboratory Pseudomonas strain allows growth on phenol, owing to expression of this enzyme and the chromosomally encoded ortho-cleavage pathway. This system, in conjunction with six plasmids that each expressed all but one of the polypeptides, was used to demonstrate that all six polypeptides are required for growth on phenol. << Less

  J. Bacteriol. 172:6826-6833(1990) [PubMed] [EuropePMC]