BIOL 26 |
| Nitrobenzene 1,2-dioxygenase (NBDO) and 2-nitrotoluene 2,3-dioxygenase (2NTDO) are critical enzymes that facilitate growth of Comamonas sp. strain JS765 and Acidovorax sp. strain JS42 on nitrobenzene and 2-nitrotoluene, respectively. Both NBDO and 2NTDO catalyze the initial step in degradation by attacking the nitro-substituted carbon, forming catechols from both nitrobenzene and 2-nitrotoluene. Although NBDO and 2NTDO are 95% identical in sequence, they exhibit different specificities towards nitroaromatic compounds. To identify amino acids responsible for specificity differences, gene fragments encoding wild-type and active-site mutants of NBDO and 2NTDO were exchanged. Activities of the resultant chimeras were measured using naphthalene, nitrobenzene, mononitrotoluenes, and dinitrotoluenes as substrates. Differences in the relative product ratios observed with the wild-type, active-site mutants, and hybrid chimeras revealed that specific residues within the active site, as well as regions distal to the substrate binding pockets of NBDO and 2NTDO influence the specificity of these enzymes towards nitroaromatic compounds. |
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Frontiers in Chemical Biology
5:00 PM-7:00 PM, Sunday, August 19, 2007 BCEC -- Exhibit Hall - B2, Poster
Division of Biological Chemistry |