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Nat Protoc. 2006;1(2):604-13. Epub 2006 Jul 6.

Tagging recombinant proteins with a Sel-tag for purification, labeling with electrophilic compounds or radiolabeling with 11C.

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Medical Nobel Institute for Biochemistry, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, SE-17177 Stockholm, Sweden.


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.

[Indexed for MEDLINE]

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