Exploiting the 21st amino acid-purifying and labeling proteins by selenolate targeting

Nat Methods. 2004 Oct;1(1):61-6. doi: 10.1038/nmeth707. Epub 2004 Sep 29.


Selenium is essential to human life and occurs in selenoproteins as selenocysteine (Sec), the 21st amino acid. The selenium atom endows selenocysteine with unique biochemical properties, including a low pK(a) and a high reactivity with many electrophilic agents. Here we describe the introduction of selenocysteine into recombinant non-selenoproteins produced in Escherichia coli, as part of a small tetrapeptide motif at the C terminus. This selenocysteine-containing motif could subsequently be used as a protein tag for purification of the recombinant protein, selenolate-targeted labeling with fluorescent compounds or radiolabeling with either gamma-emitting (75)Se or short-lived positron emitters such as (11)C. The results presented here thus show how a wide range of biotechnological applications can be developed starting from the insertion of selenocysteine into proteins.

Publication types

  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cloning, Molecular / methods
  • Escherichia coli / genetics
  • Escherichia coli / metabolism
  • Escherichia coli Proteins / chemistry
  • Escherichia coli Proteins / genetics
  • Escherichia coli Proteins / isolation & purification*
  • Escherichia coli Proteins / metabolism*
  • Mutagenesis, Site-Directed
  • Protein Engineering / methods*
  • Recombinant Fusion Proteins / chemistry
  • Recombinant Fusion Proteins / isolation & purification*
  • Recombinant Fusion Proteins / metabolism*
  • Selenocysteine / chemistry
  • Selenocysteine / genetics
  • Selenocysteine / isolation & purification*
  • Selenocysteine / metabolism*
  • Staining and Labeling / methods


  • Escherichia coli Proteins
  • Recombinant Fusion Proteins
  • Selenocysteine