MDP-1 is a new and distinct member of the haloacid dehalogenase family of aspartate-dependent phosphohydrolases.
MDP-1 is a eukaryotic magnesium-dependent acid phosphatase with little sequence homology to previously characterized phosphatases. The presence of a conserved motif (Asp-X-Asp-X-Thr) in the N terminus of MDP-1 suggested a relationship to the haloacid dehalogenase (HAD) superfamily, which contains a number of magnesium-dependent acid phosphatases. These phosphatases utilize an aspartate nucleophile and contain a number of conserved active-site residues and hydrophobic patches, which can be plausibly aligned with conserved residues in MDP-1. Seven site-specific point mutants of MDP-1 were produced by modifying the catalytic aspartate, serine, and lysine residues to asparagine or glutamate, alanine, and arginine, respectively. The activity of these mutants confirms the assignment of MDP-1 as a member of the HAD superfamily. Detailed comparison of the sequence of the 15 MDP-1 sequences from various organisms with other HAD superfamily sequences suggests that MDP-1 is not closely related to any particular member of the superfamily. The crystal structures of several HAD family enzymes identify a domain proximal to the active site responsible for important interactions with low molecular weight substrates. The absence of this domain or any other that might perform the same function in MDP-1 suggests an "open" active site capable of interactions with large substrates such as proteins. This suggestion was experimentally confirmed by demonstration that MDP-1 is competent to catalyze the dephosphorylation of tyrosine-phosphorylated proteins.
Selengut
J D
JD
Laboratory of Biochemistry, National Heart, Lung and Blood Institute, Building 50-2347, National Institutes of Health, 50 South Drive, Bethesda, Maryland 20892-8012, USA. selengut@nih.gov
D020816:Amino Acid Motifs / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D001224:Aspartic Acid / Q000737:chemistry*; D020134:Catalytic Domain / Q000235:genetics; D006801:Humans; D006867:Hydrolases / Q000737:chemistry / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D005810:Multigene Family; D016297:Mutagenesis, Site-Directed; D010749:Phosphoprotein Phosphatases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000071636:Protein Phosphatase 2C; D017434:Protein Structure, Tertiary / Q000235:genetics; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D001224:Aspartic Acid; D006867:Hydrolases; D010749:Phosphoprotein Phosphatases; D000071636:Protein Phosphatase 2C; D017027:Protein Tyrosine Phosphatases; C522354:MDP1 protein, human; C522359:Mdp1 protein, mouse; C034507:2-haloacid dehalogenase