FIELD: biotechnology. SUBSTANCE: polypeptide showing increased activity as compared with the known gamma-interferon analogues is prepared after exchange of two nucleotides in codon encoding Ser-54 reading from Cys at N-terminus of nonprocessed gamma-interferon. As a result, mutant gene encodes polypeptide which distincts from the natural gamma-interferon by exchange of Ser-54 for Asp. For expression of mutant gene in E. coli plasmid (molecular mass is 2.92 Md; 4421 base pairs) was constructed. This plasmid contains large fragment Eco RI-Pst I of plasmid pBR 322 (size is 3940 b. p.), fragment of Eco RI-Pst I with gene (481 b. p.), tetracycline resistance gene as a genetic marker, and the recognition sites by restriction endonucleases located at the following distance from Eco RI-site: Hind III 29 b. p. Bam HI - 375 b. p. Pvu II 2068 b. p. Pst I 3609 b. p. Eco RI 4079 b. p. and recognition sites of Sal I were located from Eco RI by 651 and 3941 b. p. Strain-producer of this polypeptide E. coli ВКПМ$ 5943 is obtained as a result of transformation E. coli MH-1 with plasmid pS54. The level of mutant interferon expression is 38% of total cell protein. Method is used for recombinant interferons preparing. EFFECT: preparing DNA fragment indicated above. 4 cl, 5 dwg
