Caspase-3 Regulatory Mechanisms: Difference between revisions

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Scott Eron, Banyuhay P. Serrano, Yunlong Zhao, Jaime Prilusky, Michal Harel, Alexander Berchansky

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 === Exosite and Allosteric Site===
-Caspases have similar structure of active site. Exosite that could be utilized to improve activity has been found in caspase-7 (Boucher, Blais et al. 2012). Caspase-7 also has an inhibitory allosteric site that could bind with small molecule FICA, presenting a zymogen-like conformation (Hardy, Lam et al. 2004).
+Since all caspases have very similar active site chemistry, other regions in the protein that can confer either activation or inhibition to the enzyme needs to be explored.  For example, exosites in caspase-7 have been identified and was observed to improve activity (Boucher, Blais et al. 2012). Caspase-7 also has an inhibitory allosteric site that could bind with the small molecule FICA, resulting in a zymogen-like conformation (Hardy, Lam et al. 2004) and abolishing activity.
-Although there is no evident exosite found in caspase-3, some allosteric sites, (most of which are located on the dimer interface,) has been studied by mutagenesis. Some of mutant residues can modulate the activity of caspase-3 or even procaspase-3. The procaspase-3 was detected only little activity because the orientation of ILA (prematured L2 loop) and ILB loop cannot form an active site pocket (Bose, Pop et al. 2003).
+Although there are still no evident exosites found in caspase-3, some allosteric sites, most of which are located on the dimer interface, have been interrogated by mutagenesis and was shown to modulate the activity of caspase-3 or even procaspase-3. Although only procaspase-3 was detected only with little activity because the orientation of ILA (prematured L2 loop) and ILB loop cannot form an active site pocket, it is sill quite interesting to discover how these mutations are able to rescue activity of the zymogen form (Bose, Pop et al. 2003).
-V266E is a mutation that improves caspase-3 activity dramatically. Even in the uncleavable procaspase-3 (D5A, D26A, D175A), V266E mutant zymogen is also pseudo-activated (60-fold activity). Interestingly, V266E does not change a lot conformation around active site in the active caspase-3. Based on the crystal structure, L2’ loop is partially disorder at 185’-180’. This active procaspase-3 cannot be inhibited by endogenous XIAP like normal cleaved caspase-3. So it provides us an option for apoptosis stimuli with intrinsic efficiency.
+One interesting mutation, V266E, improves caspase-3 activity dramatically. Even in the uncleavable procaspase-3 (D5A, D26A, D175A), V266E mutant zymogen is still pseudo-activated, showing a 60-fold increase in activity. Intriguingly, V266E does not undergo a lot of conformational changes around the active site in its cleaved form. Based on the crystal structure of this mutant, the L2’ loop is partially disordered at 185’-180’. Moreover, this active procaspase-3 variant cannot be inhibited by endogenous XIAP like the normal cleaved caspase-3. So it provides us an option for apoptosis stimuli with intrinsic efficiency.
-It was found recently that many other mutant residues on the dimer interface might play an important role on inhibition of caspase-3 through manipulating the hydrogen bond or remote talking across whole dimer, like V266H, Y197C, E124A.
+It was found recently that changing other critical residues (V266H, Y197C, E124A) on the dimer interface might play an important role on inhibition of caspase-3 by altering hydrogen bond patterns or through a relay of subtle conformational changes that remote talking across whole dimer, like .