Structure and Function Analysis of Peptide Antagonists of Melanoma Inhibitor of Apoptosis (ML-IAP)

• Published in: Biochemistry (Easton) Vol. 42; no. 27; pp. 8223 - 8231
• Main Authors: Franklin, Matthew C, Kadkhodayan, Saloumeh, Ackerly, Heidi, Alexandru, Daniela, Distefano, Mark D, Elliott, Linda O, Flygare, John A, Mausisa, Grace, Okawa, David C, Ong, Danny, Vucic, Domagoj, Deshayes, Kurt, Fairbrother, Wayne J
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 15.07.2003
• Subjects: Adaptor Proteins, Signal Transducing; Amino Acid Sequence; Carrier Proteins - chemistry; Carrier Proteins - genetics; Carrier Proteins - physiology; Crystallography, X-Ray; Genetic Linkage; Inhibitor of Apoptosis Proteins; Models, Molecular; Molecular Sequence Data; Neoplasm Proteins - chemistry; Neoplasm Proteins - genetics; Neoplasm Proteins - physiology; Sequence Homology, Amino Acid; Structure-Activity Relationship; X Chromosome
• ISSN: 0006-2960; 1520-4995
• DOI: 10.1021/bi034227t

Melanoma inhibitor of apoptosis (ML-IAP) is a potent anti-apoptotic protein that is upregulated in a number of melanoma cell lines but not expressed in most normal adult tissues. Overexpression of IAP proteins, such as ML-IAP or the ubiquitously expressed X-chromosome-linked IAP (XIAP), in human cancers has been shown to suppress apoptosis induced by a variety of stimuli. Peptides based on the processed N-terminus of Smac/DIABLO can negate the ability of overexpressed ML-IAP or XIAP to suppress drug-induced apoptosis. Such peptides have been demonstrated to bind to the single baculovirus IAP repeat (BIR) of ML-IAP and the third BIR of XIAP with similar high affinities (∼0.5 μM). Herein, we use phage-display of naïve peptide libraries and synthetic peptides to investigate the peptide-binding properties of ML-IAP-BIR and XIAP-BIR3. X-ray crystal structures of ML-IAP-BIR in complex with Smac- and phage-derived peptides, together with peptide structure−activity-relationship data, indicate that the peptides can be modified to provide increased binding affinity and selectivity for ML-IAP-BIR relative to XIAP-BIR3. For instance, substitution of Pro3‘ in the Smac-based peptide (AVPIAQKSE) with (2S,3S)-3-methylpyrrolidine-2-carboxylic acid [(3S)-methyl-proline] results in a peptide with 7-fold greater affinity for ML-IAP-BIR and about 100-fold specificity for ML-IAP-BIR relative to XIAP-BIR3.