Petosa C, Masters S C, Bankston L A, Pohl J, Wang B, Fu H, Liddington R C
Department of Biochemistry, University of Leicester, Leicester LE1 7RH, United Kingdom.
J Biol Chem. 1998 Jun 26;273(26):16305-10. doi: 10.1074/jbc.273.26.16305.
14-3-3 proteins bind a variety of molecules involved in signal transduction, cell cycle regulation and apoptosis. 14-3-3 binds ligands such as Raf-1 kinase and Bad by recognizing the phosphorylated consensus motif, RSXpSXP, but must bind unphosphorylated ligands, such as glycoprotein Ib and Pseudomonas aeruginosa exoenzyme S, via a different motif. Here we report the crystal structures of the zeta isoform of 14-3-3 in complex with two peptide ligands: a Raf-derived phosphopeptide (pS-Raf-259, LSQRQRSTpSTPNVHMV) and an unphosphorylated peptide derived from phage display (R18, PHCVPRDLSWLDLEANMCLP) that inhibits binding of exoenzyme S and Raf-1. The two peptides bind within a conserved amphipathic groove on the surface of 14-3-3 at overlapping but distinct sites. The phosphoserine of pS-Raf-259 engages a cluster of basic residues (Lys49, Arg56, Arg60, and Arg127), whereas R18 binds via the amphipathic sequence, WLDLE, with its two acidic groups coordinating the same basic cluster. 14-3-3 is dimeric, and its two peptide-binding grooves are arranged in an antiparallel fashion, 30 A apart. The ability of each groove to bind different peptide motifs suggests how 14-3-3 can act in signal transduction by inducing either homodimer or heterodimer formation in its target proteins.
14-3-3蛋白可结合多种参与信号转导、细胞周期调控和细胞凋亡的分子。14-3-3通过识别磷酸化共有基序RSXpSXP来结合诸如Raf-1激酶和Bad等配体，但必须通过不同的基序结合未磷酸化的配体，如糖蛋白Ib和铜绿假单胞菌外毒素S。在此，我们报道了14-3-3的ζ亚型与两种肽配体形成复合物的晶体结构：一种源自Raf的磷酸肽（pS-Raf-259，LSQRQRSTpSTPNVHMV）和一种源自噬菌体展示的未磷酸化肽（R18，PHCVPRDLSWLDLEANMCLP），后者可抑制外毒素S和Raf-1的结合。这两种肽在14-3-3表面保守的两亲性凹槽内重叠但不同的位点结合。pS-Raf-259的磷酸丝氨酸与一组碱性残基（Lys49、Arg56、Arg60和Arg127）结合，而R18通过两亲性序列WLDLE结合，其两个酸性基团与同一碱性簇配位。14-3-3是二聚体，其两个肽结合凹槽以反平行方式排列，相距30埃。每个凹槽结合不同肽基序的能力表明了14-3-3如何通过诱导其靶蛋白形成同二聚体或异二聚体来参与信号转导。
