title: Construction and flow cytometric screening of targeted enzyme libraries.
abstract: Herein, we describe a methodology for the construction of targeted libraries intended to modify the substrate specificity of proteases expressed on the cell surface of Escherichia coli. The native outer membrane protease, OmpT, is used as a model system. The protocol relies on gene assembly using oligonucleotides and is easily adaptable to any enzyme in which information is available on the putative active site residues. Increasingly complex libraries can be generated in a systematic manner and screened using flow cytometry (fluorescence-activated cell sorting, FACS) for variants displaying altered function. Furthermore, if the substrate-binding pockets have not been elucidated, a protocol for partial multi-site saturation library construction is presented that allows for sampling a large number of residues, while maintaining an appropriate level of protein function. The entire procedure, from start to finish, should take approximately 2-3 weeks.
authors.affiliation: Institute for Cell and Molecular Biology, University of Texas, Austin, TX, USA.
authors.forename: Navin
authors.initials: N
authors.lastname: Varadarajan
authors.forename: Jason R
authors.initials: JR
authors.lastname: Cantor
authors.forename: George
authors.initials: G
authors.lastname: Georgiou
authors.forename: Brent L
authors.initials: BL
authors.lastname: Iverson
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D020134:Catalytic Domain / Q000235:genetics; D002462:Cell Membrane / Q000201:enzymology; D004798:Enzymes / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D005434:Flow Cytometry / Q000379:methods*; D008958:Models, Molecular; D010447:Peptide Hydrolases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D015202:Protein Engineering; D013379:Substrate Specificity
chemical_list: D001425:Bacterial Outer Membrane Proteins; D004798:Enzymes; D029968:Escherichia coli Proteins; C499588:ompT protein, E coli; D010447:Peptide Hydrolases