CRYSTAL-STRUCTURE OF THE ZETA-ISOFORM OF THE 14-3-3 PROTEIN

THE 14-3-3 family of proteins have recently been identified as regulat ory elements in intracellular signalling pathways(1): 14-3-3 proteins bind to oncogene and proto-oncogene products, including c-Raf-1 (refs 2-5), c-Bcr (ref. 6) and polyomavirus middle-T antigen(7); overexpress ion of 14-3-3 activates Raf kinase in yeast(2,3) and induces meiotic m aturation in Xenopus oocytes(5). Here we report the crystal structure of the major isoform of mammalian 14-3-3 proteins at 2.9 Angstrom reso lution. Each subunit of the dimeric protein consists of a bundle of ni ne antiparallel helices that form a palisade around an amphipathic gro ove. The groove is large enough to accommodate a tenth helix, and we p ropose that binding to an amphipathic helix represents a general mecha nism for the interaction of 14-3-3 with diverse cellular proteins. The residues in the dimer interface and the putative ligand-binding surfa ce are invariant among vertebrates, yeast and plants, suggesting a con servation of structure and function throughout the 14-3-3 family.