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C2 domain in the Active BCR (Breakpoint cluster region) Related protein The ABR protein is similar to the breakpoint cluster region protein. It has homology to guanine nucleotide exchange proteins and GTPase-activating proteins (GAPs). ABR is expressed primarily in the brain, but also includes non-neuronal tissues such as the heart. It has been associated with human diseases such as Miller-Dieker syndrome in which mental retardation and malformations of the heart are present. ABR contains a RhoGEF domain and a PH-like domain upstream of its C2 domain and a RhoGAP domain downstream of this domain. A few members also contain a Bcr-Abl oncoprotein oligomerization domain at the very N-terminal end. Splice variants of ABR have been identified. ABR is found in a wide variety of organisms including chimpanzee, dog, mouse, rat, fruit fly, and mosquito. The C2 domain was first identified in PKC. C2 domains fold into an 8-standed beta-sandwich that can adopt 2 structural arrangements: Type I and Type II, distinguished by a circular permutation involving their N- and C-terminal beta strands. Many C2 domains are Ca2+-dependent membrane-targeting modules that bind a wide variety of substances including bind phospholipids, inositol polyphosphates, and intracellular proteins. Most C2 domain proteins are either signal transduction enzymes that contain a single C2 domain, such as protein kinase C, or membrane trafficking proteins which contain at least two C2 domains, such as synaptotagmin 1. However, there are a few exceptions to this including RIM isoforms and some splice variants of piccolo/aczonin and intersectin which only have a single C2 domain. C2 domains with a calcium binding region have negatively charged residues, primarily aspartates, that serve as ligands for calcium ions. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",