Cold adaptation of a psychrophilic chitinase: a mutagenesis study
The gene encoding chitinase Ar ChiB from the Antarctic Arthrobacter sp. TAD20 has been expressed in Escherichia coli and the recombinant enzyme purified to homogeneity. In an effort to engineer cold‐adapted biocatalysts through rational redesign to operate at elevated temperatures, we performed seve...
| Published in: | Protein Engineering Design and Selection |
|---|---|
| Main Authors: | , , , |
| Format: | Text |
| Language: | English |
| Published: |
Oxford University Press
2003
|
| Subjects: | |
| Online Access: | http://peds.oxfordjournals.org/cgi/content/short/16/7/497 https://doi.org/10.1093/protein/gzg069 |
| Summary: | The gene encoding chitinase Ar ChiB from the Antarctic Arthrobacter sp. TAD20 has been expressed in Escherichia coli and the recombinant enzyme purified to homogeneity. In an effort to engineer cold‐adapted biocatalysts through rational redesign to operate at elevated temperatures, we performed several mutations aiming to increase the rigidity of the molecular edifice of the selected psychrophilic chitinase. The mutations were designed on the basis of a homology‐based three‐dimensional model of the enzyme, and included an attempt to introduce a salt bridge (mutant N198K) and replacements of selected Gly residues by either Pro (mutants G93P, G254P) or Gln (G406Q). Mutant N198K resulted in a more stable protein (Δ T m = 0.6°C). Mutant G93P exhibited a Δ T m of 1.2°C, while mutants G254P and G406Q exhibited decreased stability. We conclude that the effect of mutating Gly residues on enzyme stability is rather complex and can only be understood in the context of the structural environment. Kinetic and spectroscopic analysis of these enzyme variants revealed that the kinetic parameters k cat and K m have been significantly modified. |
|---|