Various apoptotic signals can activate caspases 3 and 7 by triggering the L2 loop cleavage of their proenzymes. These two enzymes have highly similar structures and functions, and serve as apoptotic executioners. The structures of caspase 7 and procaspase 7 differ significantly in the conformation of the loops constituting the active site, indicating that the enzyme undergoes a large structural change during activation. To define the role of the leucine residue on the L2 loop, which shows the largest movement during enzyme activation but has not yet been studied, Leu168 of caspase 3 and Leu191 of caspase 7 were mutated. Kinetic analysis indicated that the mutation of the leucine residues sometimes improved the Km but also greatly decreased the kcat, resulting in an overall decrease in enzyme activity. The tryptophan fluorescence change at excitation/emission=280/350 nm upon L2–L2′ loop cleavage was found to be higher in catalytically active mutants, including the corresponding wild-type caspase, than in the inactive mutants. The crystal structures of the caspase 3 mutants were solved and compared with that of wild-type. Significant alterations in the conformations of the L1 and L4 loops were found. These results indicate that the leucine residue on the L2 loop has an important role in maintaining the catalytic activity of caspases 3 and 7.
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Research Article|
March 12 2012
Molecular insight into the role of the leucine residue on the L2 loop in the catalytic activity of caspases 3 and 7
Hyo Jin Kang;
Hyo Jin Kang
*Nanobiotechnology Division, University of Science and Technology (UST), Yuseong, Daejeon, 305–806, Korea
†BioNanotechnology Research Center, KRIBB, Yuseong, Daejeon, 305–806, Korea
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Young-mi Lee;
Young-mi Lee
†BioNanotechnology Research Center, KRIBB, Yuseong, Daejeon, 305–806, Korea
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Myeong Seon Jeong;
Myeong Seon Jeong
*Nanobiotechnology Division, University of Science and Technology (UST), Yuseong, Daejeon, 305–806, Korea
†BioNanotechnology Research Center, KRIBB, Yuseong, Daejeon, 305–806, Korea
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Moonil Kim;
Moonil Kim
†BioNanotechnology Research Center, KRIBB, Yuseong, Daejeon, 305–806, Korea
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Kwang-Hee Bae;
Kwang-Hee Bae
‡Medical Proteomics Research Center, KRIBB, Yuseong, Daejeon, 305–806, Korea
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Seung Jun Kim;
Seung Jun Kim
‡Medical Proteomics Research Center, KRIBB, Yuseong, Daejeon, 305–806, Korea
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Sang J. Chung
Sang J. Chung
1
*Nanobiotechnology Division, University of Science and Technology (UST), Yuseong, Daejeon, 305–806, Korea
†BioNanotechnology Research Center, KRIBB, Yuseong, Daejeon, 305–806, Korea
1To whom correspondence should be addressed (email sjchung@kribb.re.kr).
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Publisher: Portland Press Ltd
Received:
January 19 2012
Revision Received:
February 02 2012
Accepted:
February 06 2012
Accepted Manuscript online:
February 06 2012
Online ISSN: 1573-4935
Print ISSN: 0144-8463
© The Authors Journal compilation © 2012 Biochemical Society
2012
Biosci Rep (2012) 32 (3): 305–313.
Article history
Received:
January 19 2012
Revision Received:
February 02 2012
Accepted:
February 06 2012
Accepted Manuscript online:
February 06 2012
Citation
Hyo Jin Kang, Young-mi Lee, Myeong Seon Jeong, Moonil Kim, Kwang-Hee Bae, Seung Jun Kim, Sang J. Chung; Molecular insight into the role of the leucine residue on the L2 loop in the catalytic activity of caspases 3 and 7. Biosci Rep 1 June 2012; 32 (3): 305–313. doi: https://doi.org/10.1042/BSR20120009
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