This entry includes a group of VQ motif-containing proteins from plants, including MKS1 (VQ21, At3g18690) and VQ8/17/18/20/25 from Arabidopsis.In general, Arabidopsis VQPs interacted specifically with the C-terminal WRKY domains of group I and the sole WRKY domains of group IIc WRKY transcription factors [, ]. Arabidopsis VQPs reported to control stress responses include the calmodulin (CaM)-binding protein CamBP25 and VQ9, which regulate osmotic and salinity tolerance, respectively, the sigma factor binding proteins SIB1 and SIB2, which act as activators of WRKY33 in plant defence, and the negative regulator of the jasmonate defence pathway [].
The C2 domain is one of the most prevalent eukaryotic lipid-binding domains deployed in diverse functional contexts. Distinct versions of the C2 domain have been recognized, the classical C2, the PI3K-type, the tensin-type, the B9-type, the DOCK-type, the NT-type and the Aida-type. Despite their limited sequence similarity, all C2 domains contain at their core a compact β-sandwich composed of two four-stranded β-sheets with highly variable inter-strand regions that might contain one or more α-helices. One feature that is highly conserved in the C2 domains is the pair of hydrophobic residues on the upper part of the β-sheet, which are involved in imparting a curvature of the sheet that allows formation of a concave ligand-binding area [].This entry represents a family of B9-type C2 domain containing proteins, found in ciliary basal body associated proteins. Although its specific function is unknown, a cilia-specific role has been suggested for the poorly characterised B9-type C2 domain [, , ].Some proteins known to contain a B9-type C2 domain are listed below:Mammalian Tectonic-like complex member MKS1 (also known as Meckel syndrome 1 , MKS1). The tectonic-like complex is localised at the transition zone of primary cilia and acts as a barrier that prevents diffusion of transmembrane proteins between the cilia and plasma membranes. It is involved in centrosome migration to the apical cell surface during early ciliogenesis [, , ]. The homologue in Drosophila melanogaster is required for ciliary structure and function [, ]. Mammalian proteins B9D1 and B9D2. B9D1 is required for ciliogenesis and sonic hedgehog/SHH signaling [, ].
