title: Highly homologous proteins exert opposite biological activities by using different interaction interfaces.
abstract: We present a possible molecular basis for the opposite activity of two homologues proteins that bind similar ligands and show that this is achieved by fine-tuning of the interaction interface. The highly homologous ASPP proteins have opposite roles in regulating apoptosis: ASPP2 induces apoptosis while iASPP inhibits it. The ASPP proteins are regulated by an autoinhibitory interaction between their Ank-SH3 and Pro domains. We performed a detailed biophysical and molecular study of the Pro - Ank-SH3 interaction in iASPP and compared it to the interaction in ASPP2. We found that iASPP Pro is disordered and that the interaction sites are entirely different: iASPP Ank-SH3 binds iASPP Pro via its fourth Ank repeat and RT loop while ASPP2 Ank-SH3 binds ASPP2 Pro via its first Ank repeat and the n-src loop. It is possible that by using different moieties in the same interface, the proteins can have distinct and specific interactions resulting in differential regulation and ultimately different biological activities.
authors.affiliation: Institute of Chemistry, The Hebrew University of Jerusalem, Safra Campus Givat Ram, Jerusalem 91904, Israel.
authors.forename: Anat Iosub
authors.initials: AI
authors.lastname: Amir
authors.affiliation: Institute of Chemistry, The Hebrew University of Jerusalem, Safra Campus Givat Ram, Jerusalem 91904, Israel.
authors.forename: Martijn
authors.initials: M
authors.lastname: van Rosmalen
authors.affiliation: Institute of Chemistry, The Hebrew University of Jerusalem, Safra Campus Givat Ram, Jerusalem 91904, Israel.
authors.forename: Guy
authors.initials: G
authors.lastname: Mayer
authors.affiliation: Wolfson Centre for Applied Structural Biology, The Hebrew University of Jerusalem, Safra Campus Givat Ram, Jerusalem 91904, Israel.
authors.forename: Mario
authors.initials: M
authors.lastname: Lebendiker
authors.affiliation: Wolfson Centre for Applied Structural Biology, The Hebrew University of Jerusalem, Safra Campus Givat Ram, Jerusalem 91904, Israel.
authors.forename: Tsafi
authors.initials: T
authors.lastname: Danieli
authors.affiliation: Institute of Chemistry, The Hebrew University of Jerusalem, Safra Campus Givat Ram, Jerusalem 91904, Israel.
authors.forename: Assaf
authors.initials: A
authors.lastname: Friedler
mesh_terms: D000595:Amino Acid Sequence; D017089:Ankyrin Repeat; D051017:Apoptosis Regulatory Proteins / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D002846:Chromatography, Affinity; D005454:Fluorescence Polarization; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000378:metabolism; D064267:Intrinsically Disordered Proteins / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D017386:Sequence Homology, Amino Acid; D018909:src Homology Domains
chemical_list: D051017:Apoptosis Regulatory Proteins; D047908:Intracellular Signaling Peptides and Proteins; D064267:Intrinsically Disordered Proteins; D010455:Peptides