Sandbox/ caspase-3 regulation

Exosite and Allosteric SiteExosite and Allosteric Site

Anything in this section will appear adjacent to the 3D structure and will be scrollable. 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). 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). 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. 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. For instance, V266H inhibit caspase-3 activity totally, but the double mutation Y197C/V266H the activity is rescued.

spinqualitylabelsall models Structure of HMG-CoA reductase (PDB entry 1dq8) Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image

Natural InhibitorsNatural Inhibitors

X-linked inhibitor of apoptosis proteins (XIAP) contains the second baculovirus IAP repeat domain (BIR2) targeting caspase-3 and caspase-7.

Reference:

Bose, K., C. Pop, et al. (2003). "An uncleavable procaspase-3 mutant has a lower catalytic efficiency but an active site similar to that of mature caspase-3." Biochemistry 42(42): 12298-12310.

Boucher, D., V. Blais, et al. (2012). "Caspase-7 uses an exosite to promote poly(ADP ribose) polymerase 1 proteolysis." Proc Natl Acad Sci U S A 109(15): 5669-5674.

Hardy, J. A., J. Lam, et al. (2004). "Discovery of an allosteric site in the caspases." Proc Natl Acad Sci U S A 101(34): 12461-12466.