Protein engineering ofDe novo protein with predesigned structure and activity

Thede novo protein albebetin has been engineered (J. Mol. Biol. 1992,225, 927–931) to form a predesigned tertiary fold that has not yet been observed in natural proteins. Analysis of albebetin expressed in a cell-free system and inEscherichia coli revealed its compactness, relative stability, and the secondary structure close to the predesigned one. The blast-transforming biological activity of human interferon was grafted to albebetin by attachment of an eight amino acid interferon fragment to the N-terminus of albebetin next to its first methionine residue. The chimeric protein was expressed in a wheat germ cell-free translation system and tested for its structural properties, receptor binding, and biological activity. According to the tests, albebetin incorporating the active interferon fragment has a compact and relatively stable structure, and binds the murine thymocyte recep or effectively. It activates the blast transformation reaction of thymo yte cells even more efficiently than human interferon at low concentrations.