A novel low-molecular-mass dual-specificity phosphatase, LDP-2, with a naturally occurring substitution that affects substrate specificity.
We have identified a novel dual-specificity phosphatase (DSP), called LDP-2 (low-molecular-mass DSP-2), composed of 220 amino acid residues showing high sequence homology to VHR and LDP-1/TMDP, which belong to a family of DSPs with low molecular masses. The LDP-2 gene is ubiquitously expressed, and LDP-2 is localized in the cytoplasm. The main structural feature of LDP-2 is that the serine-156 residue located in the common active site sequence motif, HCXXGXXRS, for DSP is naturally substituted with an alanine residue. The recombinant LDP-2 protein showed extremely low phosphatase activity towards p-nitrophenyl phosphate (pNPP). Back-mutation of Ala-156 in LDP-2 to a serine (A156S mutation) conferred significant phosphatase activity towards pNPP. However, both LDP-2 and LDP-2 (A156S) exhibited substantial phosphatase activities towards both phospho-seryl/threonyl and -tyrosyl residues of myelin basic protein, with similar specific activities. Ala-156 of LDP-2 might be crucially involved in the recognition of a physiological substrate. We analyzed the effect of VHR and LDP-2 on mitogen-activated protein kinases (MAPKs) in vivo. We first found that VHR inhibits the activation of p38 as well as ERK and JNK, with similar efficiency. Under the conditions used, LDP-2 specifically suppressed JNK activation.
Division of Biochemical Oncology and Immunology, Institute for Genetic Medicine, Hokkaido University, Kita-ku, Sapporo 060-0815, Japan.
Koji
K
Nakamura
Kan
K
Tanoue
Takeshi
T
Satoh
Mutsuhiro
M
Takekawa
Masahiko
M
Watanabe
Hiroshi
H
Shima
Kunimi
K
Kikuchi
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019556:COS Cells; D003001:Cloning, Molecular; D018076:DNA, Complementary; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016296:Mutagenesis; D010766:Phosphorylation; D054648:Protein Phosphatase 2; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
D018076:DNA, Complementary; D011994:Recombinant Proteins; D054648:Protein Phosphatase 2; D017027:Protein Tyrosine Phosphatases; C473865:low-molecular-mass dual-specificity phosphatase-2