title: The C. elegans SYS-1 protein is a bona fide beta-catenin.
abstract: C. elegans SYS-1 has key functional characteristics of a canonical beta-catenin, but no significant sequence similarity. Here, we report the SYS-1 crystal structure, both on its own and in a complex with POP-1, the C. elegans TCF homolog. The two structures possess signature features of canonical beta-catenin and the beta-catenin/TCF complex that could not be predicted by sequence. Most importantly, SYS-1 bears 12 armadillo repeats and the SYS-1/POP-1 interface is anchored by a conserved salt-bridge, the "charged button." We also modeled structures for three other C. elegans beta-catenins to predict the molecular basis of their distinct binding properties. Finally, we generated a phylogenetic tree, using the region of highest structural similarity between SYS-1 and beta-catenin, and found that SYS-1 clusters robustly within the beta-catenin clade. We conclude that the SYS-1 protein belongs to the beta-catenin family and suggest that additional divergent beta-catenins await discovery.
authors.affiliation: Department of Biological Structure, University of Washington, Seattle, WA 98195-7420, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Liu
authors.forename: Bryan T
authors.initials: BT
authors.lastname: Phillips
authors.forename: Maria F
authors.initials: MF
authors.lastname: Amaya
authors.forename: Judith
authors.initials: J
authors.lastname: Kimble
authors.forename: Wenqing
authors.initials: W
authors.lastname: Xu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry* / Q000378:metabolism*; D018360:Crystallography, X-Ray; D003598:Cytoskeletal Proteins / Q000737:chemistry / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism; D006609:High Mobility Group Proteins / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D011485:Protein Binding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D014157:Transcription Factors / Q000737:chemistry* / Q000378:metabolism*; D051176:beta Catenin / Q000737:chemistry / Q000378:metabolism*
chemical_list: D029742:Caenorhabditis elegans Proteins; D003598:Cytoskeletal Proteins; D004268:DNA-Binding Proteins; D006609:High Mobility Group Proteins; C502083:Sys-1 protein, C elegans; D014157:Transcription Factors; C120104:WRM-1 protein, C elegans; D051176:beta Catenin; C096787:pop-1 protein, C elegans