Structural analysis of 14-3-3 phosphopeptide complexes identifies a dual role for the nuclear export signal of 14-3-3 in ligand binding.
We have solved the high-resolution X-ray structure of 14-3-3 bound to two different phosphoserine peptides, representing alternative substrate-binding motifs. These structures reveal an evolutionarily conserved network of peptide-protein interactions within all 14-3-3 isotypes, explain both binding motifs, and identify a novel intrachain phosphorylation-mediated loop structure in one of the peptides. A 14-3-3 mutation disrupting Raf signaling alters the ligand-binding cleft, selecting a different phosphopeptide-binding motif and different substrates than the wild-type protein. Many 14-3-3: peptide contacts involve a C-terminal amphipathic alpha helix containing a putative nuclear export signal, implicating this segment in both ligand and Crm1 binding. Structural homology between the 14-3-3 NES structure and those within I kappa B alpha and p53 reveals a conserved topology recognized by the Crm1 nuclear export machinery.
Rittinger
K
K
Divison of Protein Structure, National Institute for Medical Research, London, United Kingdom.
Budman
J
J
Xu
J
J
Volinia
S
S
Cantley
L C
LC
Smerdon
S J
SJ
Gamblin
S J
SJ
Yaffe
M B
MB
D048948:14-3-3 Proteins; D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D002467:Cell Nucleus / Q000378:metabolism; D016384:Consensus Sequence; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D004330:Drosophila; D004791:Enzyme Inhibitors / Q000737:chemistry; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010748:Phosphopeptides / Q000737:chemistry* / Q000378:metabolism; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry* / Q000378:metabolism; D012441:Saccharomyces cerevisiae; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014446:Tyrosine 3-Monooxygenase
D048948:14-3-3 Proteins; D004791:Enzyme Inhibitors; D010748:Phosphopeptides; D020033:Protein Isoforms; D011506:Proteins; D014446:Tyrosine 3-Monooxygenase