Biophysical characterization of mutants of Bacillus subtilis lipase evolved for thermostability: Factors contributing to increased activity retention
Augustyniak, W.; Brzezinska, A.A.; Pijning, Tjaard; Wienk, H.L.J.; Boelens, R.; Dijkstra, Bauke W.; Reetz, M.T.
(2012) Protein Science, volume 21, issue 4, pp. 487 - 497
(Article)
Abstract
Previously, Lipase A from Bacillus subtilis was subjected to in vitro directed evolution using iterative saturation mutagenesis, with randomization sites chosen on the basis of the highest B-factors available from the crystal structure of the wild-type (WT) enzyme. This provided mutants that, unlike WT enzyme, retained a large part of
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their activity after heating above 65 C and cooling down. Here, we subjected the three best mutants along with the WT enzyme to biophysical and biochemical characterization. Combining thermal inactivation profiles, circular dichroism, X-ray structure analyses and NMR experiments revealed that mutations of surface amino acid residues counteract the tendency of Lipase A to undergo precipitation under thermal stress. Reduced precipitation of the unfolding intermediates rather than increased conformational stability of the evolved mutants seems to be responsible for the activity retention
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Keywords: Aggregation, Directed evolution, Iterative saturation mutagenesis, Lipase, Thermal inactivation, acid lipase, amino acid, bacterial enzyme, mebrane protein, mutant protein, article, Bacillus subtilis, circular dichroism, controlled study, cooling, crystal structure, enzyme analysis, enzyme conformation, enzyme structure, in vitro study, nonhuman, nuclear magnetic resonance spectroscopy, precipitation, priority journal, protein unfolding, randomization, structure analysis, temperature stress, thermostability, X ray analysis
ISSN: 0961-8368
Publisher: Cold Spring Harbor Laboratory Press
(Peer reviewed)