InterPro domain: IPR007656

The GTD-binding domain is a plant-specific protein-protein interaction domain.It emerged in primitive land plants and founded a multigene family that isconserved in all flowering plants. Proteins with GTD-binding domains fall intofour groups, where group 1-3 contain the GTD-binding domain at the C-terminalhalf of the protein and one (group 2) or more (group1) predicted transmembranedomains, or an endoplasmic reticulum signal peptide (group 3) at the N-terminus, whereas group 4 contains the GTD-binding domain near the N terminus.GTD-binding domain proteins may constitute a family of myosin receptors, whichare associated with the surface of specific plant organelles, bind to theglobular tail domain (GTD) of myosin motor proteins, and thereby promoteactin-dependent organelle motility. It seems likely that myosin binding is acommon property of the GTD-binding domain, whereas the ability of FLOURY1 tobind maize-specific zeins is a specific feature of this endoplasmic reticulum(ER)-associated protein.

The GTD-binding domain is predicted to adopt a coiled-coil structure.

Some proteins known to contain a GTD-binding domain are listed below:

• Maize FLOURY1 (FL1), which belongs to group 1. Its GTD-binding domain facilitates the localization of 22kDa alpha-zein [ 1 ].
• Arabidopsis myosin binding (MyoB) proteins 1-6 and 7, which belong respectively to group 3 and 4. They bind to myosin XI [ 2 ].
• Tobacco RAC5 interacting subapical pollen tube protein (RISAP), which belongs to group 3. It binds via its GTD-binding domain to the GTD domain of a pollen tube myosin XI [ 3 ].
• Lily LLP13, which belongs to group 3. It is likely a cytoskeleton-binding protein that binds with intermediate filaments (IFs) that potentially exist in pollen tubes [ 4 ].

1. The maize floury1 gene encodes a novel endoplasmic reticulum protein involved in zein protein body formation. Plant Cell 19, 2569-82
2. Identification of myosin XI receptors in Arabidopsis defines a distinct class of transport vesicles. Plant Cell 25, 3022-38
3. RISAP is a TGN-associated RAC5 effector regulating membrane traffic during polar cell growth in tobacco. Plant Cell 26, 4426-47
4. Characterization of a lily anther-specific gene encoding cytoskeleton-binding glycoproteins and overexpression of the gene causes severe inhibition of pollen tube growth. Planta 240, 525-37