title: Structure and function analysis of peptide antagonists of melanoma inhibitor of apoptosis (ML-IAP).
abstract: 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 (approximately 0.5 microM). 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.
authors.affiliation: Department of Protein Engineering, Genentech, Inc., One DNA Way, South San Francisco, California 94080, USA.
authors.forename: Matthew C
authors.initials: MC
authors.lastname: Franklin
authors.forename: Saloumeh
authors.initials: S
authors.lastname: Kadkhodayan
authors.forename: Heidi
authors.initials: H
authors.lastname: Ackerly
authors.forename: Daniela
authors.initials: D
authors.lastname: Alexandru
authors.forename: Mark D
authors.initials: MD
authors.lastname: Distefano
authors.forename: Linda O
authors.initials: LO
authors.lastname: Elliott
authors.forename: John A
authors.initials: JA
authors.lastname: Flygare
authors.forename: Grace
authors.initials: G
authors.lastname: Mausisa
authors.forename: David C
authors.initials: DC
authors.lastname: Okawa
authors.forename: Danny
authors.initials: D
authors.lastname: Ong
authors.forename: Domagoj
authors.initials: D
authors.lastname: Vucic
authors.forename: Kurt
authors.initials: K
authors.lastname: Deshayes
authors.forename: Wayne J
authors.initials: WJ
authors.lastname: Fairbrother
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D018360:Crystallography, X-Ray; D008040:Genetic Linkage; D051034:Inhibitor of Apoptosis Proteins; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D013329:Structure-Activity Relationship; D014960:X Chromosome
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C419866:BIRC7 protein, human; D002352:Carrier Proteins; D051034:Inhibitor of Apoptosis Proteins; D009363:Neoplasm Proteins