Board, PhilipCoggan, MarjorieWatson, SarahGage, PeterDulhunty, Angela2015-12-132015-12-131357-2725http://hdl.handle.net/1885/85472We have examined the biochemical and functional properties of the recently identified, uncharacterised CLIC-2 protein. Sequence alignments showed that CLIC-2 has a high degree of sequence similarity with CLIC-1 and some similarity to the omega class of glutathione transferases (GSTO). A homology model of CLIC-2 based on the crystal structure of CLIC-1 suggests that CLIC-2 belongs to the GST structural family but, unlike the GSTs, CLIC-2 exists as a monomer. It also has an unusual enzyme activity profile. While the CXXC active site motif is conserved between CLIC-2 and the glutaredoxins, no thiol transferase activity was detected. In contrast, low glutathione peroxidase activity was recorded. CLIC-2 was found to be widely distributed in tissues including heart and skeletal muscle. Functional studies showed that CLIC-2 inhibited cardiac ryanodine receptor Ca2+ release channels in lipid bilayers when added to the cytoplasmic side of the channels and inhibited Ca2+ release from cardiac sarcoplasmic reticulum vesicles. The inhibition of RyR channels was reversed by removing CLIC-2 from the solution or by adding an anti-CLIC-2 antibody. The results suggest that one function of CLIC-2 might be to limit Ca2+ release from internal stores in cells.Keywords: calcium channel; glutaredoxin; protein; protein clic 2; ryanodine receptor; transferase; unclassified drug; animal tissue; article; biochemistry; calcium transport; controlled study; crystal structure; cytoplasm; enzyme activity; heart; lipid bilayer; non CLIC proteins; Cytoplasmic Ca2+ regulation; Glutathione transferase; Ryanodine receptor Ca2+ channels200410.1016/j.biocel.2004.01.0262015-12-12