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Open Access Research article

Widespread presence of "bacterial-like" PPP phosphatases in eukaryotes

Alexandra V Andreeva12 and Mikhail A Kutuzov12

Author Affiliations

1 Research School of Biological and Molecular Sciences, Oxford Brookes University, Headington, Oxford OX3 OBP, UK

2 Present address: University of Illinois, College of Medicine, Department of Pharmacology, 835 S. Wolcott Ave, Chicago, IL 60612, USA

BMC Evolutionary Biology 2004, 4:47  doi:10.1186/1471-2148-4-47

Published: 19 November 2004

Abstract

Background

In eukaryotes, PPP (

    p
rotein
    p
hosphatase
    P
) family is one of the two known protein phosphatase families specific for Ser and Thr. The role of PPP phosphatases in multiple signaling pathways in eukaryotic cell has been extensively studied. Unlike eukaryotic PPP phosphatases, bacterial members of the family have broad substrate specificity or may even be Tyr-specific. Moreover, one group of bacterial PPPs are diadenosine tetraphosphatases, indicating that bacterial PPP phosphatases may not necessarily function as protein phosphatases.

Results

We describe the presence in eukaryotes of three groups of expressed genes encoding "non-conventional" phosphatases of the PPP family. These enzymes are more closely related to bacterial PPP phosphatases than to the known eukaryotic members of the family. One group, found exclusively in land plants, is most closely related to PPP phosphatases from some α-Proteobacteria, including Rhizobiales, Rhodobacterales and Rhodospirillaceae. This group is therefore termed

    Rhi
zobiales /
    Rh
odobacterales
/
    Rh
odospirillaceae
-
    l
ike
    ph
osphatases, or Rhilphs. Phosphatases of the other group are found in Viridiplantae, Rhodophyta, Trypanosomatidae, Plasmodium and some fungi. They are structurally related to phosphatases from psychrophilic bacteria Shewanella and Colwellia, and are termed
    She
wanella
-
    l
ike
    ph
osphatases, or Shelphs. Phosphatases of the third group are distantly related to ApaH, bacterial diadenosine tetraphosphatases, and are termed
    A
paH-
    l
ike
    ph
osphatases, or Alphs. Patchy distribution of Alphs in animals, plants, fungi, diatoms and kinetoplasts suggests that these phosphatases were present in the common ancestor of eukaryotes but were independently lost in many lineages. Rhilphs, Shelphs and Alphs form PPP clades, as divergent from "conventional" eukaryotic PPP phosphatases as they are from each other and from major bacterial clades. In addition, comparison of primary structures revealed a previously unrecognised (I/L/V)D(S/T)G motif, conserved in all bacterial and "bacterial-like" eukaryotic PPPs, but not in "conventional" eukaryotic and archaeal PPPs.

Conclusions

Our findings demonstrate that many eukaryotes possess diverse "bacterial-like" PPP phosphatases, the enzymatic characteristics, physiological roles and precise evolutionary history of which have yet to be determined.