The functional mutational landscape of the lacZ gene
Marc A. Beal,
Matthew J. Meier,
Angela Dykes,
Carole L. Yauk,
Iain B. Lambert,
Francesco Marchetti
Affiliations
Marc A. Beal
Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, ON K1A 0K9, Canada
Matthew J. Meier
Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, ON K1A 0K9, Canada
Angela Dykes
Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, ON K1A 0K9, Canada; Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
Carole L. Yauk
Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, ON K1A 0K9, Canada; Department of Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
Iain B. Lambert
Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
Francesco Marchetti
Environmental Health Science and Research Bureau, Healthy Environments and Consumer Safety Branch, Health Canada, Ottawa, ON K1A 0K9, Canada; Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada; Corresponding author
Summary: The lacZ gene of Escherichia coli encodes β-galactosidase (β-gal), a lactose metabolism enzyme of the lactose operon. Previous chemical modification or site-directed mutagenesis experiments have identified 21 amino acids that are essential for β-gal catalytic activity. We have assembled over 10,000 lacZ mutations from published studies that were collected using a positive selection assay to identify mutations in lacZ that disrupted β-gal function. We analyzed 6,465 independent lacZ mutations that resulted in 2,732 missense mutations that impaired β-gal function. Those mutations affected 492 of the 1,023 lacZ codons, including most of the 21 previously known residues critical for catalytic activity. Most missense mutations occurred near the catalytic site and in regions important for subunit tetramerization. Overall, our work provides a comprehensive and detailed map of the amino acid residues affecting the structure and catalytic activity of the β-gal enzyme.
