EMBODYING A STABLE ALPHA-HELICAL PROTEIN-STRUCTURE THROUGH EFFICIENT CHEMICAL LIGATION VIA THIOETHER FORMATION

A new approach was developed to embody the alpha-helical protein struc ture having an arbitrary combination and arrangement of helices by the successive ligation of a haloacetyl peptide segment with a cysteinyl peptide. A four-helix-bundle protein was efficiently constructed by th e repetitive ligation of a-helical peptide segments. The use of HPLC-p urified unprotected peptide segments facilitated the purification of t he intermediates to afford the highly homogenous desired protein. The use of the bromoacetyl moiety and the chlaroacetyl moiety for the liga tion was judged to make no difference in practice. A trial of introduc ing an additional intramolecular disulfide cross-link was also examine d. The resulting protein showed high stability in the chaotropic and t hermal denaturation and in enzymatic degradation. (C) 1997 Elsevier Sc ience Ltd.