title: Metal-free and Ca2+-bound structures of a multidomain EF-hand protein, CBP40, from the lower eukaryote Physarum polycephalum.
abstract: Acellular slime mold, Physarum polycephalum, has a unique wound-healing system. When cytoplasm of plasmodia is exposed to extracellular fluid, calcium binding protein 40 (CBP40) seals damaged areas, forming large aggregates Ca(2+) dependently. Part of the CBP40 is truncated at the N terminus by a proteinase in plasmodia (CBP40delta), which does not aggregate in the Ca(2+)-bound form. Here we report the crystal structures of CBP40delta in both the metal-free and the Ca(2+)-bound states. Both structures consist of three domains: coiled-coil, intervening, and EF-hand. The topology of the EF-hand domain is similar to that of calpain. The N-terminal half of CBP40Delta interacts with the C-terminal EF-hands through a large hydrophobic interface, necessary for high Ca(2+) affinity. Conformational change upon Ca(2+) binding is small; however, the structure of CBP40delta provides novel insights into the mechanism of Ca(2+)-dependent oligomerization.
authors.affiliation: Department of Applied Biological Chemistry, Graduate School of Agricultural and Life Sciences, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan.
authors.forename: Wakana
authors.initials: W
authors.lastname: Iwasaki
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Sasaki
authors.forename: Akio
authors.initials: A
authors.lastname: Nakamura
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Kohama
authors.forename: Masaru
authors.initials: M
authors.lastname: Tanokura
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002118:Calcium / Q000737:chemistry* / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D002147:Calmodulin / Q000737:chemistry / Q000235:genetics; D002154:Calpain / Q000737:chemistry / Q000235:genetics; D008670:Metals / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D015800:Protozoan Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D016415:Sequence Alignment; D013552:Swine
chemical_list: C406924:CBP40 protein, Physarum; D002135:Calcium-Binding Proteins; D002147:Calmodulin; D008670:Metals; D015800:Protozoan Proteins; D002154:Calpain; D002118:Calcium