HIGH THERMAL-STABILITY AND COLD-DENATURATION OF AN ARTIFICIAL POLYPEPTIDE

An amphipathic polypeptide, P-n, with a tandemly repeated LKELPEKL seq uence including a proline every eight residues, as well as a series of shorter peptides having the same sequence, P-2, P-3, P-4, P-5 and P,, were synthesized. Their conformation in aqueous solution was mainly s tudied by CD. At low temperature, these peptides and polypeptide are c ompletely unordered and undergo a reversible transition leading to a p artly alpha-helical structure upon heating. Such behavior has been dem onstrated for a few proteins by other authors and has been called cold -denaturation. The transition temperature of the polypeptide is close to 20 degrees C. The conformational change does not depend on concentr ation, indicating a monomolecular process. The high-temperature struct ure seems to be compact as for globular proteins. A model of folded st ructure is proposed from experimental data and from molecular modellin g studies. (C) Munksgaard 1996.