Myotubularian 1 and related proteins Pleckstrin Homology-Glucosyltransferases, Rab-like GTPase
MTM1, MTMR1, and MTMR2 are members of the myotubularin protein phosphatase gene family. They contain a N-terminal PH-GRAM domain, a Rac-induced recruitment domain (RID) domain, an active PTP domain, a SET-interaction domain, and a C-terminal coiled-coil region. In addition MTMR1 (Myotubularian related 1 protein) and MTMR2 (Myotubularian related 2 protein) contain a C-terminal PDZ domain. Mutations in MTMR2 are a cause of Charcot-Marie-Tooth disease type 4B, an autosomal recessive demyelinating neuropathy. The protein can self-associate and form heteromers with MTMR5 and MTMR12. Myotubularin-related proteins are a subfamily of protein tyrosine phosphatases (PTPs) that dephosphorylate D3-phosphorylated inositol lipids. The GRAM domain, found in myotubularins, glucosyltransferases, and other putative membrane-associated proteins, is part of a larger motif with a pleckstrin homology (PH) domain fold. The GRAM domain, found in myotubularins, glucosyltransferases, and other putative membrane-associated proteins, is part of a larger motif with a pleckstrin homology (PH) domain fold. The PH domain family possesses multiple functions including the ability to bind phosphoinositides via its beta1/beta2, beta3/beta4, and beta6/beta7 connecting loops and to other proteins. However, no phosphoinositide binding sites have been found for the MTMRs to date.
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