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Protein Ser/Thr phosphatases PPEF interact with calmodulin
Mikhail A Kutuzov1, Olga V Solov'eva, Alexandra V Andreeva
1Laboratoire de Biophysique Moléculaire et Cellulaire URA CNRS No. 520, Département de Biologie Moléculaire et Structurale, CEA-Grenoble, 38054 Grenoble cedex 9, France. m.kutuzov@usa.net
Biochemical and Biophysical Research Communications
|June 8, 2002
Summary
New research reveals mammalian protein phosphatases with EF-hand domains (PPEF) bind calmodulin (CaM) in a calcium-dependent manner, distinct from calcineurin. This suggests a dual regulatory mechanism for PPEF phosphatase activity.
Area of Science:
- Molecular Biology
- Biochemistry
- Cell Signaling
Background:
- Cytoplasmic calcium (Ca2+) and calmodulin (CaM) are known regulators of protein dephosphorylation, primarily through calcineurin.
- The recent discovery of EF-hand domain-containing protein phosphatases (PPEF/rdgC) suggests additional Ca2+-dependent phosphatases exist.
- The N-terminal domains of PPEF/rdgC phosphatases were hypothesized to contain CaM-binding sites.
Purpose of the Study:
- To investigate the interaction between PPEF phosphatases and CaM.
- To determine if PPEF phosphatases possess CaM-binding sites and if this interaction is calcium-dependent.
- To elucidate the potential regulatory mechanisms of PPEF phosphatases by Ca2+ and CaM.
Main Methods:
- Yeast two-hybrid system for in vivo interaction studies.
- Surface plasmon resonance (SPR) for in vitro binding affinity and kinetics.
- Analysis of specific protein fragments containing IQ motifs.
Main Results:
- The entire human PPEF2 protein was found to interact with CaM in vivo.
- The N-terminal domain of PPEF2 demonstrated Ca2+-dependent binding to CaM in vitro with nanomolar affinity.
- Specific fragments of PPEF1 and PPEF2, containing IQ motifs, were sufficient for Ca2+-dependent CaM interaction both in vivo and in vitro.
Conclusions:
- Mammalian CaM-binding protein Ser/Thr phosphatases, distinct from calcineurin, have been identified.
- PPEF phosphatases exhibit Ca2+-dependent interaction with CaM via their N-terminal domains.
- The activity of PPEF phosphatases may be dually regulated by Ca2+ through its C-terminal domain and CaM binding to the N-terminal domain.