title: Co-crystallization with conformation-specific designed ankyrin repeat proteins explains the conformational flexibility of BCL-W.
abstract: BCL-W is a member of the BCL-2 family of anti-apoptotic proteins. A key event in the regulation of apoptosis is the heterodimerization between anti-apoptotic and pro-apoptotic family members, which involves a conserved surface-exposed groove on the anti-apoptotic proteins. Crystal structures of the ligand binding-competent conformation exist for all anti-apoptotic family members, with the exception of BCL-W, due to the flexibility of the BCL-W groove region. Existing structures had suggested major deviations of the BCL-W groove region from the otherwise structurally highly related remaining anti-apoptotic family members. To capture its ligand binding-competent conformation by counteracting the conformational flexibility of the BCL-W groove, we had selected high-affinity groove-binding designed ankyrin repeat proteins (DARPins) using ribosome display. We now determined two high-resolution crystal structures of human BCL-W in complex with different DARPins at resolutions 1.5 and 1.85Å, in which the structure of BCL-W is virtually identical, and BCL-W adopts a conformation extremely similar to the ligand-free conformation of its closest relative BCL-XL in both structures. However, distinct differences to all previous BCL-W structures are evident, notably in the ligand-binding region. We provide the first structural explanation for the conformational flexibility of the BCL-W groove region in comparison to other BCL-2 family members. Due to the importance of the anti-apoptotic BCL-2 family as drug targets, the presented crystal structure of ligand binding-competent BCL-W may serve as a valuable basis for structure-based drug design in the future and provides a missing piece for the structural characterization of this protein family.
authors.affiliation: Biochemisches Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
authors.forename: Johannes
authors.initials: J
authors.lastname: Schilling
authors.affiliation: Biochemisches Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
authors.forename: Jendrik
authors.initials: J
authors.lastname: Schöppe
authors.affiliation: Biozentrum, Universität Basel, Klingelbergstrasse 50/70, CH-4056 Basel, Switzerland.
authors.forename: Evelyn
authors.initials: E
authors.lastname: Sauer
authors.affiliation: Biochemisches Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland. Electronic address: plueckthun@bioc.uzh.ch.
authors.forename: Andreas
authors.initials: A
authors.lastname: Plückthun
mesh_terms: D051017:Apoptosis Regulatory Proteins / Q000737:chemistry* / Q000378:metabolism*; D018360:Crystallography, X-Ray; D006801:Humans; D008958:Models, Molecular; D011485:Protein Binding; D011487:Protein Conformation
chemical_list: D051017:Apoptosis Regulatory Proteins; C491073:BCL2L2 protein, human
keywords: BCL-W; DARPins; anti-apoptotic BCL-2 family; apoptosis; ligand binding-competent conformation