Structure of the anchor-domain of myristoylated and non-myristoylated HIV-1 Nef protein

Negative factor (Nef) is a regulatory myristoylated protein of human immuno deficiency virus (HIV) that has a two-domain structure consisting of an anc hor domain and a core domain separated by a specific cleavage site of the H IV proteases. For structural analysis, the HIV-1 Nef anchor domain (residue s 2-57) was synthesized with a myristoylated and nonmyristoylated N terminu s. The structures of the two peptides were studied by H-1 NMR spectroscopy and a structural model was obtained by restrained molecular dynamic simulat ions. The non-myristoylated peptide does not have a unique, compactly folde d structure but occurs in a relatively extended conformation. The only rath er well-defined canonical secondary structure element is a short two-turn a lpha-helix (H2) between Arg35 and Gly41. A tendency for another helical sec ondary structure element (H1) can be observed for the arginine-rich region (Arg17 to Arg22). Myristoylation of the N-terminal glycine residue leads to stabilization of both helices, H1 and H2. The first helix in the arginine- rich region is stabilized by the myristoylation and now contains residues P ro14 to Arg22. The second helix appears to be better defined and to contain more residues (Ala33 to Gly41) than in the absence of myristoylation. In a ddition, the hydrophobic N-terminal myristic acid residue interacts closely with the side-chain of Trp5 and thereby forms a loop with Gly2, Gly3 and L ys4 in the kink region. This interaction could possibly be disturbed by pho sphorylation of a nearby serine residue, and modifiy the characteristic mem brane interactions of the HIV-1 Nef anchor domain. (C) 1999 Academic Press.