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C2 domain second repeat present in RAS p21 protein activator 3 (RasA3) RasA3 are members of GTPase activating protein 1 (GAP1), a Ras-specific GAP, which suppresses Ras function by enhancing the GTPase activity of Ras proteins resulting in the inactive GDP-bound form of Ras. In this way it can control cellular proliferation and differentiation. RasA3 contains an N-terminal C2 domain, a Ras-GAP domain, a plextrin homology (PH)-like domain, and a Bruton's Tyrosine Kinase (BTK) zinc binding domain. 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. This cd contains the second C2 repeat, C2B, and has a type-I topology. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",