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KMID : 0545120160260122179
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Journal of Microbiology and Biotechnology
2016 Volume.26 No. 12 p.2179 ~ p.2183
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Residue Y70 of the Nitrilase Cyanide Dihydratase from Bacillus pumilus Is Critical for Formation and Activity of the Spiral Oligomer
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Park Jason M.
Ponder Christian M.
Sewell Trevor B.
Benedik Michael J.
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Abstract
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Nitrilases pose attractive alternatives to the chemical hydrolysis of nitrile compounds. The activity of bacterial nitrilases towards substrate is intimately tied to the formation of large spiral-shaped oligomers. In the nitrilase CynD (cyanide dihydratase) from Bacillus pumilus, mutations in a predicted oligomeric surface region altered its oligomerization and reduced its activity. One mutant, CynD Y70C, retained uniform oligomer formation however it was inactive, unlike all other inactive mutants throughout that region all of which significantly perturbed oligomer formation. It was hypothesized that Y70 is playing an additional role necessary for CynD activity beyond influencing oligomerization. Here, we performed saturation mutagenesis at residue 70 and demonstrated that only tyrosine or phenylalanine is permissible for CynD activity. Furthermore, we show that other residues at this position are not only inactive, but have altered or disrupted oligomer conformations. These results suggest that Y70’s essential role in activity is independent of its role in the formation of the spiral oligomer.
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KEYWORD
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nitrilase, cyanide dihydratase, quaternary structure, cyanide, oligomerization surface, bioremediation
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