Chloride Intracellular Channel Protein 2: Difference between revisions
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== Links between CLIC2 and the GST superfamily members == | == Links between CLIC2 and the GST superfamily members == | ||
GST | ===GST=== | ||
CLIC2 belongs to the glutathione S-transferase (GST) superfamily because it adopts the same secondary structure as GSTs. Between CLIC proteins and GSTs, there are four key residues conserved. A cis-proline residue (Pro 71 in CLIC2) that allows a properly binding site for GSH in all GSTs, an aspartic acid (Asp 183 in CLIC2) that allows interaction between the N-terminal helix and a cap and two glycines that are involved in structural role. The first obvious difference between CLIC2 and other GSTs is, as we said earlier, the fact that CLIC2 is the only one that can exist only as a monomer. | CLIC2 belongs to the glutathione S-transferase (GST) superfamily because it adopts the same secondary structure as GSTs. Between CLIC proteins and GSTs, there are four key residues conserved. A cis-proline residue (Pro 71 in CLIC2) that allows a properly binding site for GSH in all GSTs, an aspartic acid (Asp 183 in CLIC2) that allows interaction between the N-terminal helix and a cap and two glycines that are involved in structural role. The first obvious difference between CLIC2 and other GSTs is, as we said earlier, the fact that CLIC2 is the only one that can exist only as a monomer. | ||
Then, there are two other main differences between GSTs and CLICs. There is a long and highly charged loop region, called the foot loop, which we can find only in CLIC2 (from Thr 152 to Thr 180) at the base of the molecule. There is also another charged region in CLIC2 that is absent in other GST proteins. This one is composed by three acid residues in the C-terminal helix α9 (between residues 232 and 239). | Then, there are two other main differences between GSTs and CLICs. There is a long and highly charged loop region, called the foot loop, which we can find only in CLIC2 (from Thr 152 to Thr 180) at the base of the molecule. There is also another charged region in CLIC2 that is absent in other GST proteins. This one is composed by three acid residues in the C-terminal helix α9 (between residues 232 and 239). | ||
On another hand, CLIC2 has a pronounced basic wide crevice like many GST (particularly the beta and the omega classes of GSTs), called the mouth region, which is large enough to accept protein targets. There are some evidences showing that CLIC2 can have an enzymatic activity since this mouth-like region is in the same location as found in GSTs. Actually, the GST active site is composed of a groove between two domains wich forms a GSH binding site (G-site) and a binding site for hydrophobic electrophilic compounds (H-site). However, even with GSH addition in crystallization conditions, no binding of GSH by CLIC2 had been observed. This may be due to the fact that GST residues involved on binding with GSH are nearly all substituted by non conserving residues in CLIC2. Presently, we can only assume that CLIC2 has an enzymatic activity, but no GSH binding site has been discovered yet. | On another hand, CLIC2 has a pronounced basic wide crevice like many GST (particularly the beta and the omega classes of GSTs), called the mouth region, which is large enough to accept protein targets. There are some evidences showing that CLIC2 can have an enzymatic activity since this mouth-like region is in the same location as found in GSTs. Actually, the GST active site is composed of a groove between two domains wich forms a GSH binding site (G-site) and a binding site for hydrophobic electrophilic compounds (H-site). However, even with GSH addition in crystallization conditions, no binding of GSH by CLIC2 had been observed. This may be due to the fact that GST residues involved on binding with GSH are nearly all substituted by non conserving residues in CLIC2. Presently, we can only assume that CLIC2 has an enzymatic activity, but no GSH binding site has been discovered yet. | ||
CLIC’s | ===CLIC’s=== | ||
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