THE 14-3-3 PROTEIN BINDS ITS TARGET PROTEINS WITH A COMMON SITE LOCATED TOWARDS THE C-TERMINUS

The 14-3-3 protein family binds a variety of proteins in cell-signalin g pathways, but the structural elements necessary for the ligand bindi ng are poorly understood, Here we demonstrate that the 'box-1' region, which spans residues 171-213 in the eta-isoform and was previously id entified as the binding site of 14-3-3 to the phosphorylated tryptopha n hydroxylase, plays a critical role in the interaction with many targ et proteins, Using a series of truncated 14-3-3 mutants, me show that the mutant 167-213 carrying box-1 binds bacurovirus-expressed Raf-1 an d Bcr protein kinases to the similar extent as the full-length 14-3-3 in a phosphorylation-dependent manner, while the mutants lacking this region abolish the binding activity, Furthermore, the box-1 region als o appears essential for binding of 14-3-3 to more than 40 phosphoprote ins found in the brainstem extract, These results suggest that the box -1 region, consisting of helices 7 and 8 in the tertiary structure, is a common structural element whereby the 14-3-3 protein binds many, if not all, target proteins. (C) 1997 Federation of European Biochemical Societies.