NMR AND CD STUDIES ON THE CONFORMATION OF A SYNTHETIC PEPTIDE-CONTAINING EPITOPES OF THE HUMAN-IMMUNODEFICIENCY-VIRUS-1 TRANSMEMBRANE PROTEIN GP41

CD and nmr characterizations are reported for the 23-mer peptide CMC;I , corresponding to residues 577-599 of gp41, the transmembrane glycopl otein of the human immunodeficiency virus I. Concentration, temperatur e, and pH dependencies of CD and nmr spectra are indicative of self-as sociation with a consequent stabilization of secondary structural elem ents in water. The addition to the water solution of small amounts of trifluoroethanol induces a secondary structure, mostly due to the pres ence of helical elements. The amphipathic character of the helix and t he presence of three hydrophobic 4/3 heptad repeats suggest that the p eptide could be structured in a symmetric association of helices, such as in a coiled-coil structure. This behavior is discussed in terms of a possible role of this segment in the gp41 envelope oligomerization. (C) 1996 John Wiley & Sons, Inc.