[Preparation and bacterial expression of a mutant gene for human lymphotoxin]

Using the oligonucleotide directed mutagenesis, a human lymphotoxin (TNF beta) mutant gene lacking 21 N-terminal codons has been obtained. Recombinant plasmid pLT21 for expression of the mutant gene has been constructed. The mutant gene in the plasmid was placed under control of a tandem of constitutive promoters from coliphage T7. A simple procedure for isolation of recombinant protein was developed. The procedure allows to obtain the highly purified biologically active mutant protein with a good yield. During biosynthesis the recombinant protein undergoes a posttranslational processing resulted in the cleavage of N-terminal methionine and leucine residues.