S-tag
Encyclopedia
S-tag is the name of an oligopeptide
derived from pancreatic ribonuclease A (RNase A). If RNase A is digested with subtilisin
, a single peptide 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. The N-terminus of the original RNase A, also called S-peptide, consists of 20 amino acid
residues, of which only the first 15 are required for ribonuclease activity. This 15 amino acid
s long peptide is called S15 or S-tag.
The amino 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. 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 any protein
. After gene expression
, such a tagged protein can be detected by commercially available antibodies.
Oligopeptide
An oligopeptide consists of between 2 and 20 amino acids and includes dipeptides, tripeptides, tetrapeptides, pentapeptides, etc.Examples of oligopeptides include:...
derived from pancreatic ribonuclease A (RNase A). If RNase A is digested with subtilisin
Subtilisin
Subtilisin is a non-specific protease initially obtained from Bacillus subtilis.Subtilisins belong to subtilases, a group of serine proteases that initiate the nucleophilic attack on the peptide bond through a serine residue at the active site. They are physically and chemically...
, a single peptide bond
Peptide bond
This article is about the peptide link found within biological molecules, such as proteins. A similar article for synthetic molecules is being created...
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. The N-terminus of the original RNase A, also called S-peptide, consists of 20 amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
residues, of which only the first 15 are required for ribonuclease activity. This 15 amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
s long peptide is called S15 or S-tag.
The amino 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. 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 any protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
. After gene expression
Gene expression
Gene expression is the process by which information from a gene is used in the synthesis of a functional gene product. These products are often proteins, but in non-protein coding genes such as ribosomal RNA , transfer RNA or small nuclear RNA genes, the product is a functional RNA...
, such a tagged protein can be detected by commercially available antibodies.