Process for production of recombinant proteins as a soluble form

An expression vector for expression of a fusion protein, comprising:

• (1) an expression-inducible promoter sequence, wherein the expression-inducible promoter sequence is a cold-shock promoter sequence selected from the group consisting of a cspA promoter sequence, a cspB promoter sequence, a cspG promoter sequence, a cspl promoter sequence, and a csdA promoter sequence;
• (2) a first coding sequence comprising a polynucleotide encoding a polypeptide that is represented by the formula (Z)n, wherein n represents an integer from 1 to 5 and Z represents polypeptide selected from the group of:
• (a) a polypeptide comprising the amino acid sequence of SEQ ID NO:
• 1,
• (b) a polypeptide comprising an amino acid sequence that has at least 95% identity with the amino acid sequence of SEQ ID NO:
• 1, and
• (c) a polypeptide comprising an amino acid sequence that has at least 98% identity with the amino acid sequence of SEQ ID NO:
• 1, and
• that has the capacity when expressed as a fusion protein with a target protein to render said fusion protein expressible as a soluble protein;
• and
• (3) at least one restriction enzyme site that enables the insertion of a second coding sequence that comprises a polynucleotide that encodes a target protein,
• wherein the vector further comprises, on the 5′ side of the first coding sequence, a coding sequence that comprises a polynucleotide that encodes an amino acid sequence that facilitates purification, and
• wherein the expression of the fusion protein comprising the amino acid sequence that facilitates purification, the amino acid sequence of the polypeptide that is represented by the formula (Z)n and the amino acid sequence of the target protein is induced in Escherichia coli, and the fusion protein accumulates within the Escherichia coli as a soluble protein so that the fusion protein collected from within the Escherichia coli has higher solubility rate than non-(Z)n fusion protein.

A polynucleotide for expression of a fusion protein comprising

• an expression-inducible promoter sequence, wherein the expression-inducible promoter sequence is a cold-shock promoter sequence selected from the group consisting of a cspA promoter sequence, a cspB promoter sequence, a cspG promoter sequence, a cspl promoter sequence, and a csdA promoter sequence, and
• a polynucleotide that encodes the fusion protein that can be expressed as a soluble protein, comprising:
• (1) a first amino acid sequence comprising the amino acid sequence of a polypeptide that is represented by the formula (Z)n,
• wherein n represents an integer from 1 to 5 and Z represents polypeptide selected from the group of:
• (a) a polypeptide comprising the amino acid sequence of SEQ ID NO:
• 1,
• (b) a polypeptide comprising an amino acid sequence that has at least 95% identity with the amino acid sequence of SEQ ID NO:
• 1, and
• (c) a polypeptide comprising an amino acid sequence that has at least 98% identity with the amino acid sequence of SEQ ID NO:
• 1, and
• that has the capacity when expressed as a fusion protein with a target protein to render said fusion protein expressible as a soluble protein;
• and
• (2) a second amino acid sequence comprising the amino acid sequence of a target protein, wherein the polynucleotide further comprises, on the 5′ side of the first coding sequence, a coding sequence that comprises a polynucleotide that encodes an amino acid sequence that facilitates purification,
• wherein an expression for the polynucleotide which encodes the fusion protein comprising the amino acid sequence that facilitates purification, the amino acid sequence of the polypeptide that is represented by the formula (Z)n and the amino acid sequence of the target protein is induced in Escherichia coli, and the fusion protein accumulates within the Escherichia coli as a soluble protein so that the fusion protein collected from within the Escherichia coli has higher solubility rate than non-(Z)n fusion protein.