NMR structure and mutagenesis of the third Bir domain of the inhibitor of apoptosis protein XIAP.

Sun C, Cai M, Meadows RP, Xu N, Gunasekera AH, Herrmann J, Wu JC, Fesik SW
J Biol Chem. 2000 275 (43): 33777-81

PMID: 10934209 · DOI:10.1074/jbc.M006226200

The inhibitor of apoptosis proteins (IAPs) regulate the caspase family of cysteine proteases, which play an important role in the execution of programmed cell death. Human X-linked inhibitor of apoptosis protein (XIAP) is a potent inhibitor of caspases-3, -7, and -9. Here we show that the Bir3 domain is the minimal region of XIAP that is needed for potent caspase-9 inhibition. The three-dimensional structure of the Bir3 domain of XIAP, determined by NMR spectroscopy, resembles a classical zinc finger and consists of five alpha-helices, a three-stranded beta-sheet, and a zinc atom chelated to three cysteines and one histidine. The structure of the Bir3 domain is similar to that of the Bir2 domain of XIAP but differs from the previously determined structure of the Bir3 domain of MIHB. Based on site-directed mutagenesis, we have identified the regions of the Bir3 domain of XIAP that are important for inhibiting caspase-9. Despite the structural similarities of the Bir2 and Bir3 domain of XIAP, a different set of residues were found to be critical for inhibiting the individual caspases. These results suggest that XIAP inhibits caspase-3 and caspase-9 in a different manner.

MeSH Terms (13)

Amino Acid Sequence Apoptosis Caspase 9 Caspase Inhibitors Enzyme Inhibitors Magnetic Resonance Spectroscopy Molecular Sequence Data Mutagenesis, Site-Directed Proteins Protein Structure, Secondary Repetitive Sequences, Amino Acid Structure-Activity Relationship X-Linked Inhibitor of Apoptosis Protein

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