title: Structural implications of Ca2+-dependent actin-bundling function of human EFhd2/Swiprosin-1.
abstract: EFhd2/Swiprosin-1 is a cytoskeletal Ca2+-binding protein implicated in Ca2+-dependent cell spreading and migration in epithelial cells. EFhd2 domain architecture includes an N-terminal disordered region, a PxxP motif, two EF-hands, a ligand mimic helix and a C-terminal coiled-coil domain. We reported previously that EFhd2 displays F-actin bundling activity in the presence of Ca2+and this activity depends on the coiled-coil domain and direct interaction of the EFhd2 core region. However, the molecular mechanism for the regulation of F-actin binding and bundling by EFhd2 is unknown. Here, the Ca2+-bound crystal structure of the EFhd2 core region is presented and structures of mutants defective for Ca2+-binding are also described. These structures and biochemical analyses reveal that the F-actin bundling activity of EFhd2 depends on the structural rigidity of F-actin binding sites conferred by binding of the EF-hands to Ca2+. In the absence of Ca2+, the EFhd2 core region exhibits local conformational flexibility around the EF-hand domain and C-terminal linker, which retains F-actin binding activity but loses the ability to bundle F-actin. In addition, we establish that dimerisation of EFhd2 via the C-terminal coiled-coil domain, which is necessary for F-actin bundling, occurs through the parallel coiled-coil interaction.
authors.affiliation: School of Life Science, Gwangju Institute of Science and Technology (GIST), 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea.|Steitz Center for Structural Biology and Department of Chemistry, Gwangju Institute of Science and Technology (GIST), 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea.
authors.forename: Kyoung Ryoung
authors.initials: KR
authors.lastname: Park
authors.affiliation: School of Life Science, Gwangju Institute of Science and Technology (GIST), 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea.
authors.forename: Min-Sung
authors.initials: MS
authors.lastname: Kwon
authors.affiliation: School of Life Science, Gwangju Institute of Science and Technology (GIST), 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea.|Steitz Center for Structural Biology and Department of Chemistry, Gwangju Institute of Science and Technology (GIST), 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea.
authors.forename: Jun Yop
authors.initials: JY
authors.lastname: An
authors.affiliation: School of Life Science, Gwangju Institute of Science and Technology (GIST), 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea.|Steitz Center for Structural Biology and Department of Chemistry, Gwangju Institute of Science and Technology (GIST), 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea.
authors.forename: Jung-Gyu
authors.initials: JG
authors.lastname: Lee
authors.affiliation: School of Life Science, Gwangju Institute of Science and Technology (GIST), 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea.|Steitz Center for Structural Biology and Department of Chemistry, Gwangju Institute of Science and Technology (GIST), 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea.
authors.forename: Hyung-Seop
authors.initials: HS
authors.lastname: Youn
authors.affiliation: School of Life Science, Gwangju Institute of Science and Technology (GIST), 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea.|Steitz Center for Structural Biology and Department of Chemistry, Gwangju Institute of Science and Technology (GIST), 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea.
authors.forename: Youngjin
authors.initials: Y
authors.lastname: Lee
authors.affiliation: School of Life Science, Gwangju Institute of Science and Technology (GIST), 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea.|Steitz Center for Structural Biology and Department of Chemistry, Gwangju Institute of Science and Technology (GIST), 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea.
authors.forename: Jung Youn
authors.initials: JY
authors.lastname: Kang
authors.affiliation: School of Life Science, Gwangju Institute of Science and Technology (GIST), 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea.|Steitz Center for Structural Biology and Department of Chemistry, Gwangju Institute of Science and Technology (GIST), 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea.
authors.forename: Tae Gyun
authors.initials: TG
authors.lastname: Kim
authors.affiliation: School of Life Science, Gwangju Institute of Science and Technology (GIST), 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea.|Steitz Center for Structural Biology and Department of Chemistry, Gwangju Institute of Science and Technology (GIST), 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea.
authors.forename: Jia Jia
authors.initials: JJ
authors.lastname: Lim
authors.affiliation: Protein Structure Group, Korea Basic Science Institute, 162 Yeongudanji-Ro, Ochang 363-883, Republic of Korea.
authors.forename: Jeong Soon
authors.initials: JS
authors.lastname: Park
authors.affiliation: Department of Cellular and Molecular Medicine, Chosun University School of Medicine, 375 Seosuk-dong, Dong-gu, Gwangju 501-759, Republic of Korea.
authors.forename: Sung Haeng
authors.initials: SH
authors.lastname: Lee
authors.affiliation: School of Life Science, Gwangju Institute of Science and Technology (GIST), 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea.
authors.forename: Woo Keun
authors.initials: WK
authors.lastname: Song
authors.affiliation: Protein Structure Group, Korea Basic Science Institute, 162 Yeongudanji-Ro, Ochang 363-883, Republic of Korea.
authors.forename: Hae-Kap
authors.initials: HK
authors.lastname: Cheong
authors.affiliation: School of Life Science, Gwangju Institute of Science and Technology (GIST), 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea.
authors.forename: Chang-Duk
authors.initials: CD
authors.lastname: Jun
authors.affiliation: School of Life Science, Gwangju Institute of Science and Technology (GIST), 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea.|Steitz Center for Structural Biology and Department of Chemistry, Gwangju Institute of Science and Technology (GIST), 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Republic of Korea.
authors.forename: Soo Hyun
authors.initials: SH
authors.lastname: Eom
mesh_terms: D000199:Actins / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D018360:Crystallography, X-Ray; D006801:Humans; D008958:Models, Molecular; D009154:Mutation; D011485:Protein Binding; D000072417:Protein Domains; D017434:Protein Structure, Tertiary
chemical_list: D000199:Actins; D002135:Calcium-Binding Proteins; C502299:EFHD2 protein, human; D002118:Calcium