title: Structural and functional characterization ofCaenorhabditis elegansα-catenin reveals constitutive binding to β-catenin and F-actin.
abstract: Intercellular epithelial junctions formed by classical cadherins, β-catenin, and the actin-binding protein α-catenin link the actin cytoskeletons of adjacent cells into a structural continuum. These assemblies transmit forces through the tissue and respond to intracellular and extracellular signals. However, the mechanisms of junctional assembly and regulation are poorly understood. Studies of cadherin-catenin assembly in a number of metazoans have revealed both similarities and unexpected differences in the biochemical properties of the cadherin·catenin complex that likely reflect the developmental and environmental requirements of different tissues and organisms. Here, we report the structural and biochemical characterization of HMP-1, theCaenorhabditis elegansα-catenin homolog, and compare it with mammalian α-catenin. HMP-1 shares overall similarity in structure and actin-binding properties, but displayed differences in conformational flexibility and allosteric regulation from mammalian α-catenin. HMP-1 bound filamentous actin with an affinity in the single micromolar range, even when complexed with the β-catenin homolog HMP-2 or when present in a complex of HMP-2 and the cadherin homolog HMR-1, indicating that HMP-1 binding to F-actin is not allosterically regulated by the HMP-2·HMR-1 complex. The middle (i.e.M) domain of HMP-1 appeared to be less conformationally flexible than mammalian α-catenin, which may underlie the dampened effect of HMP-2 binding on HMP-1 actin-binding activity compared with that of the mammalian homolog. In conclusion, our data indicate that HMP-1 constitutively binds β-catenin and F-actin, and although the overall structure and function of HMP-1 and related α-catenins are similar, the vertebrate proteins appear to be under more complex conformational regulation.
authors.affiliation: From the School of Biological Sciences, Seoul National University, Seoul 08826, South Korea.
authors.forename: Hyunook
authors.initials: H
authors.lastname: Kang
authors.affiliation: From the School of Biological Sciences, Seoul National University, Seoul 08826, South Korea.
authors.forename: Injin
authors.initials: I
authors.lastname: Bang
authors.affiliation: the Pohang Accelerator Laboratory, Pohang, Gyeongbuk 37673, South Korea.
authors.forename: Kyeong Sik
authors.initials: KS
authors.lastname: Jin
authors.affiliation: the Department of Biophysics and Chemical Biology and.
authors.forename: Boyun
authors.initials: B
authors.lastname: Lee
authors.affiliation: From the School of Biological Sciences, Seoul National University, Seoul 08826, South Korea.|the Department of Biophysics and Chemical Biology and.|the Institute of Molecular Biology and Genetics, Seoul National University, Seoul 08826, South Korea.
authors.forename: Junho
authors.initials: J
authors.lastname: Lee
authors.affiliation: the Department of Zoology and Program in Genetics, University of Wisconsin, Madison, Wisconsin 53706.
authors.forename: Xiangqiang
authors.initials: X
authors.lastname: Shao
authors.affiliation: the Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, and.
authors.forename: Jonathon A
authors.initials: JA
authors.lastname: Heier
authors.affiliation: the Department of Cell Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, and.
authors.forename: Adam V
authors.initials: AV
authors.lastname: Kwiatkowski
authors.affiliation: the Departments of Biology.|Molecular and Cellular Physiology, and.
authors.forename: W James
authors.initials: WJ
authors.lastname: Nelson
authors.affiliation: the Department of Zoology and Program in Genetics, University of Wisconsin, Madison, Wisconsin 53706.
authors.forename: Jeff
authors.initials: J
authors.lastname: Hardin
authors.affiliation: Molecular and Cellular Physiology, and.|Structural Biology, Stanford University School of Medicine, Stanford, California 94305.
authors.forename: William I
authors.initials: WI
authors.lastname: Weis
authors.affiliation: From the School of Biological Sciences, Seoul National University, Seoul 08826, South Korea, choihj@snu.ac.kr.
authors.forename: Hee-Jung
authors.initials: HJ
authors.lastname: Choi
mesh_terms: D000199:Actins / Q000737:chemistry*; D000495:Allosteric Site; D000818:Animals; D015820:Cadherins / Q000737:chemistry*; D017173:Caenorhabditis elegans; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry*; D002448:Cell Adhesion; D018360:Crystallography, X-Ray; D003598:Cytoskeletal Proteins / Q000737:chemistry*; D005982:Glutathione Transferase / Q000378:metabolism; D056004:Molecular Dynamics Simulation; D011485:Protein Binding; D000072417:Protein Domains; D011817:Rabbits; D013329:Structure-Activity Relationship; D016596:Vinculin / Q000737:chemistry; D051178:alpha Catenin / Q000737:chemistry*; D051176:beta Catenin / Q000737:chemistry*
chemical_list: D000199:Actins; D015820:Cadherins; D029742:Caenorhabditis elegans Proteins; D003598:Cytoskeletal Proteins; C000600734:HMP-1 protein, C elegans; C442473:HMP-2 protein, C elegans; D051178:alpha Catenin; D051176:beta Catenin; C450060:hmr-1 protein, C elegans; D016596:Vinculin; D005982:Glutathione Transferase
keywords: Caenorhabditis elegans (C. elegans); HMP-1; HMP-2; X-ray crystallography; actin; cell adhesion; four helix bundle; small-angle X-ray scattering (SAXS); α-catenin (a-catenin)