title: An unconventional IAP-binding motif revealed by target-assisted iterative screening (TAIS) of the BIR3-cIAP1 domain.
abstract: Target-assisted iterative screening (TAIS) has been applied to a random phage-displayed peptide library in a search for novel ligands of the third baculovirus IAP ('inhibitors of apoptosis') repeat (BIR) domain of cIAP1. The peptides selected in the screen fall into two distinct specificity groups, one that conforms to a known IAP-binding motif (IBM) and another one that reveals a novel BIR domain interacting motif, NH(2)-SR(V/P)W. The biochemical profiling of selected sequences with synthetic peptides, which included alanine scanning and N- and C-terminal truncations as well as competition with the Smac peptide, suggests a major energetic contribution of tryptophan at the +4 position of peptide ligands to binding and identifies the latter together with the respective pocket on the BIR domain surface as a 'hot spot' of the interaction. A peptide featuring the novel motif selectively binds the full-length cIAP1 protein in cell lysates. A 'two-pocket' model of BIR domain recognition mechanism is proposed as the basis of differential BIR domain interactions with different IBMs.
authors.affiliation: The Buck Institute for Age Research, 8001 Redwood Blvd., Novato, CA 94945, USA. akourakine@buckinstitute.org
authors.forename: Alexei
authors.initials: A
authors.lastname: Kurakin
authors.forename: Dale E
authors.initials: DE
authors.lastname: Bredesen
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001667:Binding, Competitive; D002846:Chromatography, Affinity; D020650:Combinatorial Chemistry Techniques / Q000379:methods*; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000737:chemistry* / Q000378:metabolism*; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019151:Peptide Library; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D017384:Sequence Deletion
chemical_list: D051034:Inhibitor of Apoptosis Proteins; D008024:Ligands; D019151:Peptide Library; D010455:Peptides