TBC1 domain family member 1 and related proteins Phosphotyrosine-binding (PTB) domain
The TBC1D1-like members here include TBC1D1, TBC1D4 (also called Akt substrate of 160 kDa or AS160), and pollux (PLX), a calmodulin-binding protein, and are thought to have a role in regulating cell growth and differentiation. These proteins are thought to function as GTPase-activating protein for Rab family protein(s). They may play a role in the cell cycle and differentiation of various tissues. They all contain an N-terminal PTB domain, a calmodulin CBD domain, and a C-terminal TBC domain which is thought to be a GTPase activator protein of Rab-like small GTPases. Recently, TBC1D1 and TBC1D4 were recognized to potentially link the proximal signalling of insulin and/or exercise with GLUT4. TBC1D4 is thought to be involved in contraction-stimulated glucose uptake, but TBC1D4-independent mechanisms (potentially involving TBC1D1) are likely to be essential for most of the contraction's effect. PTB domains have a common PH-like fold and are found in various eukaryotic signaling molecules. This domain was initially shown to binds peptides with a NPXY motif with differing requirements for phosphorylation of the tyrosine, although more recent studies have found that some types of PTB domains can bind to peptides lack tyrosine residues altogether. In contrast to SH2 domains, which recognize phosphotyrosine and adjacent carboxy-terminal residues, PTB-domain binding specificity is conferred by residues amino-terminal to the phosphotyrosine. PTB domains are classified into three groups: phosphotyrosine-dependent Shc-like, phosphotyrosine-dependent IRS-like, and phosphotyrosine-independent Dab-like PTB domains. This cd is part of the Dab-like subgroup.
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