A systematic study was conducted with Bacillus subtilis lipase A (BSLA) to determine the effect of every single amino acid substitution on detergent tolerance. BSLA is a minimal α/β-hydrolase of 181 amino acids with a known crystal structure. It can be expressed in Escherichia coli and is biochemically well characterized. Site saturation mutagenesis resulted in a library of 3439 variants, each with a single amino acid exchange as confirmed by DNA sequencing. The library was tested against four detergents, namely SDS, CTAB, Tween 80, and sulfobetaine. Surface remodeling emerged as an effective engineering strategy to increase tolerance towards detergents. Amino acid residues that significantly affect the tolerance for each of the four detergents were identified. In summary, this systematic analysis provides an experimental dataset to help derive novel protein engineering strategies as well as to direct modeling efforts.
Keywords: Bacillus subtilis lipase A; alpha beta hydrolases; detergent effects; directed evolution; noncovalent interactions.
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