SOLUTION CONFORMATION OF A PEPTIDE FRAGMENT REPRESENTING THE 1ST ZINC-FINGER DOMAIN OF THE HIV-2 NUCLEOCAPSID PROTEIN BY CD AND NMR-SPECTROSCOPY

Standard one- and two-dimensional proton NMR techniques were used for the structural determination of an 18-residue synthetic peptide containing the amino acid sequence of the first zinc-finger domain from the gag protein of the human immunodeficiency virus type 2 (HIV-2). All resonances could be assigned by a combined use of two-dimensional correlated spectroscopy and Nuclear Overhauser Enhancement (NOE) spectroscopy carried out at two different temperatures. Qualitative analysis of NOE data reveals that this zinc complex adopts a compact, folded conformation with the presence of both type I and type II beta-turns, in agreement with circular dichroism measurements under similar physicochemical conditions. The HIV-2 fragment binds zinc tightly and stoichiometrically in a wide range of pH. In addition, these studies lead to the discovery of two sets of NMR lines, indicating that this 18-residue peptide, unlike the other retroviral zinc finger sequences, is present in solution as two slowly interconverting species.