Phosphatase Subfamily MTMR9

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Phosphatase Classification: Fold CC1: Superfamily CC1: Family Myotubularin: Subfamily MTMR9

MTMR9 is a conserved pseudophosphatase across holozoan. It regulates active phosphatases of subfamily MTMR6.


MTMR9 is found throughout holozoan. It is usually single copy per genome.

Domain Structure

MTMR9 subfamily has three domains: PH/GRAM, phosphatase domain and coiled-coil domain. The GRAM domain is similar to PH domain in structure and is found in membrane-associated proteins. As shown in MTMR3 subfamily, PH/GRAM domain can bind to phosphoinositide lipids. Coiled-coil domain has been shown to mediate the interaction between MTMR9 and members of MTMR6 in human [1, 2, 3].

Catalytic activity and functions

MTMR9 is an inactive phosphatase (pseudophosphatase). MTMR9 binds to phosphatases of MTMR6 subfamily: MTMR6 [2], MTMR7 [1], MTMR8 [3]. The interactions increase the enzymatic activity of these phosphatases. The interaction between MTMR9 and members of MTMR6 subfamily is also observed in C. elegans [4].


  1. Mochizuki Y and Majerus PW. Characterization of myotubularin-related protein 7 and its binding partner, myotubularin-related protein 9. Proc Natl Acad Sci U S A. 2003 Aug 19;100(17):9768-73. DOI:10.1073/pnas.1333958100 | PubMed ID:12890864 | HubMed [Mochizuki03]
  2. Zou J, Chang SC, Marjanovic J, and Majerus PW. MTMR9 increases MTMR6 enzyme activity, stability, and role in apoptosis. J Biol Chem. 2009 Jan 23;284(4):2064-71. DOI:10.1074/jbc.M804292200 | PubMed ID:19038970 | HubMed [zou09]
  3. Zou J, Zhang C, Marjanovic J, Kisseleva MV, Majerus PW, and Wilson MP. Myotubularin-related protein (MTMR) 9 determines the enzymatic activity, substrate specificity, and role in autophagy of MTMR8. Proc Natl Acad Sci U S A. 2012 Jun 12;109(24):9539-44. DOI:10.1073/pnas.1207021109 | PubMed ID:22647598 | HubMed [zou12]
  4. Silhankova M, Port F, Harterink M, Basler K, and Korswagen HC. Wnt signalling requires MTM-6 and MTM-9 myotubularin lipid-phosphatase function in Wnt-producing cells. EMBO J. 2010 Dec 15;29(24):4094-105. DOI:10.1038/emboj.2010.278 | PubMed ID:21076391 | HubMed [marie10]
All Medline abstracts: PubMed | HubMed