Phosphatase Subfamily egg

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Phosphatase Classification: Fold CC1: Superfamily CC1: Family PTP: Subfamily Egg


The egg subfamily is nematode specific. C. elegans has three members: egg-3, egg-4, egg-5.


The egg subfamily has a single structural domain: a CC1-fold phosphatase domain. egg-4/5 have about 200AA of unconserved sequence upstream, while egg-3 has about 200 AA of sequence with no sequence similarity beyond nematode orthologs of these genes.


All three C. elegans members are predicted to be catalytically inactive, due to loss of the cysteine or arginine of the Cx5R motif. The near-identical proteins, egg-4 and egg-5, control the oocyte- to-zygote transition by regulating signaling by the DYRK family kinase MBK-2. egg-4/egg-5 binds to MBK-2 at the substrate-binding groove of the kinase, and inhibits the ability of the kinase to bind and phosphorylate substrates, thereby inhibiting downstream signaling [1, 2, 3].


  1. Cheng KC, Klancer R, Singson A, and Seydoux G. Regulation of MBK-2/DYRK by CDK-1 and the pseudophosphatases EGG-4 and EGG-5 during the oocyte-to-embryo transition. Cell. 2009 Oct 30;139(3):560-72. DOI:10.1016/j.cell.2009.08.047 | PubMed ID:19879842 | HubMed [Cheng09]
  2. Parry JM, Velarde NV, Lefkovith AJ, Zegarek MH, Hang JS, Ohm J, Klancer R, Maruyama R, Druzhinina MK, Grant BD, Piano F, and Singson A. EGG-4 and EGG-5 Link Events of the Oocyte-to-Embryo Transition with Meiotic Progression in C. elegans. Curr Biol. 2009 Nov 3;19(20):1752-7. DOI:10.1016/j.cub.2009.09.015 | PubMed ID:19879147 | HubMed [Parry09]
  3. Tonks NK. Pseudophosphatases: grab and hold on. Cell. 2009 Oct 30;139(3):464-5. DOI:10.1016/j.cell.2009.10.008 | PubMed ID:19879835 | HubMed [Tonks09]
All Medline abstracts: PubMed | HubMed