A novel tumor necrosis factor-alpha mutant with significantly enhanced cytotoxicity and receptor binding affinity

A novel tumor necrosis factor-alpha mutant (mutant M3), in which Ser and Tyr at positions 52 and 56 were substituted by Ile and Phe, respectively, along with deletion of 7 N-terminal amino acids, was prepared and its biological activities were investigated. The mutant exhibited a 14- to 24-fold increase in the cytotoxicity relative to the wild-type TNF on various cancer cell lines. The binding affinity of the mutant to TNF-R55 and TNF-R75 receptors was over 10-fold higher than that of the wild-type. TNF-alpha and the mutant show similar CD spectra in the far-UV region, indicating that the overall structure was not influenced by the mutations. The production of highly potent TNF-alpha mutant utilizing increase of hydrophobicity in the region 52-56 may provide a structural basis for a design of optimized TNF-alpha as a therapeutic purpose.