title: Amino acids C-terminal to the 14-3-3 binding motif in CDC25B affect the efficiency of 14-3-3 binding.
abstract: The phospho-site adapter protein 14-3-3 binds to target proteins at amino acid sequences matching the consensus motif Arg-X-X-Ser/Thr-X-Pro, where the serine or threonine residue is phosphorylated and X is any amino acid. The dual-specificity phosphatase CDC25B, which is involved in cell cycle regulation, contains five 14-3-3 binding motifs, but 14-3-3 preferentially binds to the motif at Ser309 in CDC25B1 (or Ser323 in CDC25B3). In the present study, we demonstrate that amino acid residues C-terminal to the 14-3-3 binding motif strongly affect the efficiency of 14-3-3 binding. Alanine substitutions at residues downstream of the Ser309 motif dramatically reduced 14-3-3 binding, although phosphorylation of Ser309 was unaffected. We also observed that binding of endogenous 14-3-3 to mutant CDC25B occurred less efficiently than to the wild type. Mutants to which 14-3-3 cannot bind efficiently tend to be located in the nucleus, although not as specifically as the alanine substitution mutant of Ser309. These results indicate that amino acid sequences C-terminal to the consensus binding site have an important role in the efficient binding of 14-3-3 to at least CDC25B, which may partly explain why some consensus sequences are inactive as 14-3-3 binding sites.
authors: Division of Life Science, Graduate School of Science and Technology, Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa 920-1192.
authors: Sanae
authors: S
authors: Uchida
authors: Akitsugu
authors: A
authors: Kubo
authors: Ryoichi
authors: R
authors: Kizu
authors: Hitoshi
authors: H
authors: Nakagama
authors: Tsukasa
authors: T
authors: Matsunaga
authors: Yukihito
authors: Y
authors: Ishizaka
authors: Katsumi
authors: K
authors: Yamashita