%0 Journal Article
%T Conservation and divergence between cytoplasmic and muscle-specific actin capping proteins: insights from the crystal structure of cytoplasmic Cap32/34 from Dictyostelium discoideum
%A Christian Eckert
%A Agnieszka Goretzki
%A Maria Faberova
%A Martin Kollmar
%J BMC Structural Biology
%D 2012
%I BioMed Central
%R 10.1186/1472-6807-12-12
%X To elucidate structural and functional differences between cytoplasmic and sarcomercic CP variants, we have solved the atomic structure of Cap32/34 (32£¿=£¿¦Â- and 34£¿=£¿¦Á-subunit) from the cellular slime mold Dictyostelium at 2.2£¿£¿ resolution and compared it to that of chicken muscle CapZ. The two homologs display a similar overall arrangement including the attached ¦Á-subunit C-terminus (¦Á-tentacle) and the flexible ¦Â-tentacle. Nevertheless, the structures exhibit marked differences suggesting considerable structural flexibility within the ¦Á-subunit. In the ¦Á-subunit we observed a bending motion of the ¦Â-sheet region located opposite to the position of the C-terminal ¦Â-tentacle towards the antiparallel helices that interconnect the heterodimer. Recently, a two domain twisting attributed mainly to the ¦Â-subunit has been reported. At the hinge of these two domains Cap32/34 contains an elongated and highly flexible loop, which has been reported to be important for the interaction of cytoplasmic CP with actin and might contribute to the more dynamic actin-binding of cytoplasmic compared to sarcomeric CP (CapZ).The structure of Cap32/34 from Dictyostelium discoideum allowed a detailed analysis and comparison between the cytoplasmic and sarcomeric variants of CP. Significant structural flexibility could particularly be found within the ¦Á-subunit, a loop region in the ¦Â-subunit, and the surface of the ¦Á-globule where the amino acid differences between the cytoplasmic and sarcomeric mammalian CP are located. Hence, the crystal structure of Cap32/34 raises the possibility of different binding behaviours of the CP variants toward the barbed end of actin filaments, a feature, which might have arisen from adaptation to different environments.Actin is a key component in all eukaryotic cells and plays an essential role in a wide range of cellular processes, such as migration, endocytosis, cytokinesis and generation of contraction [1-4]. Actin monomers (G-actin) are able to polymeriz
%K Capping protein
%K Actin-binding
%K Dictyostelium discoideum
%K Structural flexibility
%K Cap32/34
%K CapZ
%U http://www.biomedcentral.com/1472-6807/12/12