C2 domain third repeat found in Multiple C2 domain and Transmembrane region Proteins (MCTP); plant subset. MCTPs are involved in Ca2+ signaling at the membrane. Plant-MCTPs are composed of a variable N-terminal sequence, four C2 domains, two transmembrane regions (TMRs), and a short C-terminal sequence. It is one of four protein classes that are anchored to membranes via a transmembrane region; the others being synaptotagmins, extended synaptotagmins, and ferlins. MCTPs are the only membrane-bound C2 domain proteins that contain two functional TMRs. MCTPs are unique in that they bind Ca2+ but not phospholipids. 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 third C2 repeat, C2C, and has a type-II topology.

Glutathione (GSH) peroxidase family; tetrameric selenoenzymes that catalyze the reduction of a variety of hydroperoxides including lipid peroxidases, using GSH as a specific electron donor substrate. GSH peroxidase contains one selenocysteine residue per subunit, which is involved in catalysis. Different isoenzymes are known in mammals,which are involved in protection against reactive oxygen species, redox regulation of many metabolic processes, peroxinitrite scavenging, and modulation of inflammatory processes.

probable glutathione peroxidase

phospholipid hydroperoxide glutathione peroxidase

Plant phosphoribosyltransferase C-terminal. This domain is found at the C-terminus of phosphoribosyltransferases and phosphoribosyltransferase-like proteins. It contains putative transmembrane regions. It often appears together with calcium-ion dependent C2 domains (pfam00168).