 | This articlemay containcitations that do notverify the text. Pleasecheck for citation inaccuracies.(May 2013) (Learn how and when to remove this message) |
| This article includes alist of references,related reading, orexternal links,but its sources remain unclear because it lacksinline citations. Please helpimprove this article byintroducing more precise citations.(May 2013) (Learn how and when to remove this message) |
S-tag is the name of anoligopeptide derived frompancreatic ribonuclease A (RNase A).
If RNase A is digested withsubtilisin, a singlepeptide bond is cleaved, but the resulting two products remain weakly bound to each other and the protein, called ribonuclease S, remains active although each of the two products alone shows no enzymatic activity. TheN-terminus of the original RNase A, also called S-peptide, consists of 20amino acid residues, of which only the first 15 are required for ribonuclease activity. This 15amino acids long peptide is calledS15 orS-tag.
Theamino acid sequence of the S-tag is: Lys-Glu-Thr-Ala-Ala-Ala-Lys-Phe-Glu-Arg-Gln-His-Met-Asp-Ser. It is believed that the peptide with its abundance of charged and polar residues could improve solubility of proteins it is attached to[citation needed]. Moreover, the peptide alone is thought not to fold into a distinct structure. On DNA-level the S-tag can be attached to the N- or C-terminus of anyprotein. Aftergene expression, such a tagged protein can be detected by commercially availableantibodies.
1. R.T. Raines et al., The S-Tag Fusion System for Protein Purification. Methods Enzymol. 326, 362-367 (2000)
