IDENTIFICATION OF AN ALPHA-HELICAL MOTIF SUFFICIENT FOR ASSOCIATION WITH PAPILLOMAVIRUS E6

We recently identified a cellular protein named E6BP or ERC-55 that bi nds cancer-related papillomavirus E6 proteins (Chen, J. J., Reid, C. E ., Band, V., and Androphy, E. J. (1995) Science 269, 529-531), By cons truction of a series of deletion mutants, the region of E6BP that is n ecessary and sufficient for complex formation with human papillomaviru s type 16 E6 has been mapped to a 25-amino acid domain. The correspond ing peptide was synthesized and found by nuclear magnetic resonance sp ectroscopy to bind calcium and fold into a classical helix-loop-helix EF-hand conformation. Additional deletion mutagenesis showed that 13 a mino acids that form the second alpha helix mediated E6 association. A lanine replacement mutagenesis indicated that amino acids of this heli x were most important for E6 binding. Alignment of this alpha helical E6 binding peptide with the 18-amino acid E6 binding region of E6AP (H uibregtse, J. M., Scheffner, M., and Howley, P. M. (1993) Mol. Cell. B iol. 13, 4918-4927) and the first LD repeat of another E6-binding prot ein, paxillin (Tong, X. and Howley, P. M. (1997) J. Biol. Chem. 272, 3 3373-33376), revealed substantial similarities among these E6 binding domains, The extent of homology and the mutational data define the pep tide as an E6 binding motif.