[Human tumor necrosis factor mutants: preparation and some properties]

Using polymerase chain reaction, a number of mutant genes encoding human tumor necrosis factor (TNF-alpha) with amino acid substitutions and a deletion were obtained. The mutant proteins (muteins) contained point mutations R32H, A33S, F144L, I118M, and I118A; double mutation R32H-F144L; and deletion of four amino acid residues 67-70. The mutant genes were expressed in E. coli under the control of constitutive promoters. A simple purification method for the muteins was developed and their physicochemical properties were studied. All the muteins obtained, except F144L and I118A, were shown by CD and cross-linking to from a spatial structure similar to that of the native TNF-alpha. The collection of muteins was characterized by their biological activity. Mutants R32H and A33S exerted a decreased cytotoxicity against murine fibroblast cell line L929, whereas point mutant F144L and double mutant R32H-F144L were essentially inactive.