ALPHA-HELICAL ASSEMBLY OF BIOLOGICALLY-ACTIVE PEPTIDES AND DESIGNED HELIX BUNDLE PROTEIN

The formation of alpha-helical assembly by complexing biologically act ive peptides with de novo designed protein is described. The de novo d esigned protein described here is a cystine-linked 4-helix bundle prot ein constructed with 80 amino acid residues and forms a hydrophobic co re region surrounded by 4 helices in an aqueous solution. The biologic ally active peptides, such as melittin and human growth hormone releas ing factor, contain the sequences that are able to form amphiphilic he lices. These peptides alone do not form the alpha-helix structure in a diluted solution with low ion strength. But on mixing with the design ed helix bundle protein, the peptides are strongly bound to the protei n with the induction of alpha-helical structure in the biologically ac tive peptides. The content of induced alpha-helix is in accord with th at estimated from the amphiphilic sequence. The results mean that a no vel architecture composed of alpha-helices is formed. Fluorescent and temperature-scanning measurement revealed that the alpha-helical assem bly is constructed with hydrophobic interaction. Also, it is shown by means of fluorescence depolarization that the assembly has a compact g lobular form corresponding to 1 : 1 complex. (C) 1994 John Wiley & Son s, Inc.