NMR structure and mutagenesis of the inhibitor-of-apoptosis protein XIAP.
The inhibitor-of-apoptosis (IAP) family of proteins, originally identified in baculoviruses, regulate programmed cell death in a variety of organisms. IAPs inhibit specific enzymes (caspases) in the death cascade and contain one to three modules of a common 70-amino-acid motif called the BIR domain. Here we describe the nuclear magnetic resonance structure of a region encompassing the second BIR domain (BIR2) of a human IAP family member, XIAP (also called hILP or MIHA). The structure of the BIR domain consists of a three-stranded antiparallel beta-sheet and four alpha-helices and resembles a classical zinc finger. Unexpectedly, conserved amino acids within the linker region between the BIR1 and BIR2 domains were found to be critical for inhibiting caspase-3. The absence or presence of these residues may explain the differences in caspase inhibition observed for different truncated and full-length IAPs. Our data further indicate that these residues may bind to the active site and that the BIR domain may interact with an adjacent site on the enzyme.[1]References
- NMR structure and mutagenesis of the inhibitor-of-apoptosis protein XIAP. Sun, C., Cai, M., Gunasekera, A.H., Meadows, R.P., Wang, H., Chen, J., Zhang, H., Wu, W., Xu, N., Ng, S.C., Fesik, S.W. Nature (1999) [Pubmed]
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