Abstract: By linking a peptide tag having the following amino acid sequence to a protein of interest, and then expressing the protein, the protein of interest is efficiently accumulated in a soluble fraction. X(PY)qPZ P represents proline; X represents an amino acid sequence composed of 0 to 5 amino acids independently selected from the group consisting of arginine (R), glycine (G), serine (S), lysine (K), threonine (T), leucine (L), asparagine (N), glutamine (Q), and methionine (M); Y represents an amino acid sequence composed of 1 to 4 amino acids independently selected from the group consisting of R, G; K, T, L, N, Q, and M; q represents an integer of 1 to 10; and Z represents an amino acid sequence composed of 0 to 10 amino acids independently selected from the group consisting of R, G; S K, T, L, N, Q, and M; with the proviso that the amino acid sequence of the peptide tag contains three or more Q('s), M('s), L('s), N('s), and/or T('s) in total.

Abstract: A peptide comprising the sequence shown below is added as a peptide tag to a useful protein, followed by allowing its expression. Xm(PYn)qPZr In this formula, X, Y, and Z each represent an amino acid residue independently selected from the group consisting of R, G, S, K, T, L, N, Q, and H, with the proviso that at least one Y represents K, L, N, Q, H, or R. m represents an integer of 0 to 5; n represents 1, 2, or 3; q represents an integer of 1 to 10; and r represents an integer of 0 to 10.

Abstract: A peptide comprising the sequence shown below is added as a peptide tag to a useful protein, followed by allowing its expression. Xm(PYn)qPZr In this formula, X, Y, and Z each represent an amino acid residue independently selected from the group consisting of R, G, S, K, T, L, N, Q, and H, with the proviso that at least one Y represents K, L, N, Q, H, or R. m represents an integer of 0 to 5; n represents 1, 2, or 3; q represents an integer of 1 to 10; and r represents an integer of 0 to 10.

Abstract: A peptide comprising the sequence shown below is added as a peptide tag to a useful protein, followed by allowing its expression. Xm(PYn)qPZr In this formula, X, Y, and Z each represent an amino acid residue independently selected from the group consisting of R, G, S, K, T, L, N, Q, and H, with the proviso that at least one Y represents K, L, N, Q, H, or R. m represents an integer of 0 to 5; n represents 1, 2, or 3; q represents an integer of 1 to 10; and r represents an integer of 0 to 10.

Abstract: The present invention provides an agent for controlling colibacillosis including a fusion protein comprising a subunit of Shiga toxin and a subunit of Escherichia coli heat-labile toxin.

Abstract: The present invention provides an agent for controlling Escherichia coli diarrhea comprising a Shiga toxin as an active ingredient.

Abstract: The present invention provides an agent for controlling Escherichia coli diarrhea comprising a Shiga toxin as an active ingredient.

Abstract: The present invention provides an agent for controlling colibacillosis including a fusion protein comprising a subunit of Shiga toxin and a subunit of Escherichia coli heat-labile toxin.