title: Tagging recombinant proteins with a Sel-tag for purification, labeling with electrophilic compounds or radiolabeling with 11C.
abstract: Selenocysteine (Sec; U in one-letter code) is the twenty-first naturally occurring amino acid, with a selenium atom that gives this cysteine (Cys) homolog unique biochemical properties, including a high nucleophilicity and significant reactivity with electrophilic agents. This can be used in biotechnological Sec-dependent applications. Here, we describe how Sec can be introduced into a carboxy-terminal tetrapeptide motif (-Gly-Cys-Sec-Gly-COOH, known as a Sel-tag) for recombinant proteins by tailoring the encoding gene to become compatible with the Escherichia coli selenoprotein synthesis machinery. We also describe how the Sel-tag can be used as a basis for efficient one-step protein purification, rapid Sec-targeting protein labeling with electrophilic compounds, or radiolabeling with the positron emitter 11C.
authors.affiliation: Medical Nobel Institute for Biochemistry, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-17177 Stockholm, Sweden.
authors.forename: Qing
authors.initials: Q
authors.lastname: Cheng
authors.forename: Sharon
authors.initials: S
authors.lastname: Stone-Elander
authors.forename: Elias S J
authors.initials: ES
authors.lastname: Arnér
mesh_terms: D002250:Carbon Radioisotopes; D004926:Escherichia coli; D015964:Gene Expression Regulation, Bacterial; D007553:Isotope Labeling / Q000379:methods*; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000032:analysis* / Q000737:chemistry / Q000302:isolation & purification*; D017279:Selenocysteine / Q000737:chemistry*; D051140:Selenoproteins / Q000378:metabolism
chemical_list: D002250:Carbon Radioisotopes; D011994:Recombinant Proteins; D051140:Selenoproteins; D017279:Selenocysteine