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Structural and biochemical basis of apoptotic activation by Smac/DIABLO

Nature volume 406, pages 855–862 (2000)Cite this article

Abstract

Apoptosis (programmed cell death), an essential process in the development and homeostasis of metazoans, is carried out by caspases. The mitochondrial protein Smac/DIABLO performs a critical function in apoptosis by eliminating the inhibitory effect of IAPs (inhibitor of apoptosis proteins) on caspases. Here we show that Smac/DIABLO promotes not only the proteolytic activation of procaspase-3 but also the enzymatic activity of mature caspase-3, both of which depend upon its ability to interact physically with IAPs. The crystal structure of Smac/DIABLO at 2.2 Å resolution reveals that it homodimerizes through an extensive hydrophobic interface. Missense mutations inactivating this dimeric interface significantly compromise the function of Smac/DIABLO. As in the Drosophila proteins Reaper, Grim and Hid, the amino-terminal amino acids of Smac/DIABLO are indispensable for its function, and a seven-residue peptide derived from the amino terminus promotes procaspase-3 activation in vitro. These results establish an evolutionarily conserved structural and biochemical basis for the activation of apoptosis by Smac/DIABLO.

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Figure 1: Schematic representation of Smac structure.
Figure 2: Specificity at the dimeric interface.
Figure 3: Functional significance of the dimeric interface in Smac.
Figure 4: Functional significance of the N terminus of Smac.
Figure 5: N-terminal peptides of Smac directly promote the activation of procaspase-3.
Figure 6: Model of Smac function.

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Acknowledgements

We thank D. Vaux for providing XIAP cDNA; E. Alnemri for providing caspase-3 expression vector; F. Hughson for critically reading the manuscript; and N. Hunt for secretarial assistance. This work was supported by start-up funds from Princeton University (to Y.S.) and Howard Hughes Medical Institute (to X.W.). Y.S. is a Searle Scholar and a Rita Allen Scholar.

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Authors and Affiliations

  1. Department of Molecular Biology Princeton University, Washington Road, Princeton , 08544, New Jersey, USA

    Jijie Chai, Jia-Wei Wu, Saw Kyin & Yigong Shi

  2. Howard Hughes Medical Institute and Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, 75235, Texas, USA

    Chunying Du & Xiaodong Wang

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Correspondence to Yigong Shi.

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Chai, J., Du, C., Wu, JW. et al. Structural and biochemical basis of apoptotic activation by Smac/DIABLO . Nature 406, 855–862 (2000). https://doi.org/10.1038/35022514

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