FIELD: biotechnology, genetic and protein engineering, molecular biology, biochemistry. SUBSTANCE: method of producing oxytocin is based on the use of the novel recombinant DNA pteilox4 encoding fused protein ILOX4. Its amino acid sequence consists of N-terminal (63 amino acids) sequence of human interleukin-3 and oligomer of oxytocin that contains monomer units flanked with lysine residues for specific enzymatic cleavage. Invention involves the use of the strain-producer E. coli BL21 (DE3)/pteilox4 also. This provides high level of biosynthesis of fused protein (up to 30% of total cellular protein). Recombinant plasmid pteilox4 consists of Hind III/Eco RI DNA-fragment of plasmid pTE21L3 containing promoter P8 of gene 8 of phage fd, promoter and enhancer of translation of gene 10 of phage T7, terminator of transcription of phage fd, gene encoding β-lactamase and N-terminal part of gene encoding interleukin-3 and Hind III/Eco RI-fragment that is synthetic gene of oxytocinoyl-lysine tetramer. Strain of Escherichia coli BL21 (DE3)/pteilox4 is obtained by transformation of competent cells of E. coli BL21 (DE3) with corresponding plasmid pteilox4. Strain is deposited at N VKPM B-7757. Strain of Escherichia coli BL21 (DE3)/pteilox4 is cultured in rich medium, grown cells are disrupted in buffer solution and fused protein ILOX4 is isolated. Then this protein is cleft by enzymatic method followed by or simultaneous reduction of disulfide bonds. Removal of C-terminal amino acid residue from oxytocin decapeptide formed in cleavage of fused protein is carried out either with carboxypeptidase Y (with simultaneous amidation of terminal glycine residue in oxytocine) or with carboxy-peptidase B followed by chemical amidation of terminal amino acid (glycine). Stable recombinant protein ILOX4 is obtained as result. EFFECT: simplified process, improved stability of end protein. 4 cl, 2 dwg
