Molecular and biochemical characterization of a novel actin bundling protein in Acanthamoeba.
Actin binding proteins play key roles in cell structure and movement particularly as regulators of the assembly, stability and localization of actin filaments in the cytoplasm. In the present study, a cDNA clone encoding an actin bundling protein named as AhABP was isolated from Acanthamoeba healyi, a causative agent of granulomatous amebic encephalitis. This clone exhibited high similarity with genes of Physarum polycephalum and Dictyostelium discoideum, which encode actin bundling proteins. Domain search analysis revealed the presence of essential conserved regions, i.e., an active actin binding site and 2 putative calcium binding EF-hands. Transfected amoeba cells demonstrated that AhABP is primarily localized in phagocytic cups, peripheral edges, pseudopods, and in cortical cytoplasm where actins are most abundant. Moreover, AhABP after the deletion of essential regions formed ellipsoidal inclusions within transfected cells. High-speed co-sedimentation assays revealed that AhABP directly interacted with actin in the presence of up to 10 microM of calcium. Under the electron microscope, thick parallel bundles were formed by full length AhABP, in contrast to the thin actin bundles formed by constructs with deletion sites. In the light of these results, we conclude that AhABP is a novel actin bundling protein that is importantly associated with actin filaments in the cytoplasm.
Alafag
Joanna It-Itan
JI
Department of Parasitology, Kyungpook National University School of Medicine, Daegu, Korea.
Moon
Eun-Kyung
EK
Hong
Yeon-Chul
YC
Chung
Dong-Il
DI
Kong
Hyun-Hee
HH
D000048:Acanthamoeba / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D000199:Actins / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D003001:Cloning, Molecular; D003470:Culture Media; D018076:DNA, Complementary; D020832:EF Hand Motifs; D008840:Microfilament Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D046529:Microscopy, Electron, Transmission; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D014162:Transfection
D000199:Actins; D003470:Culture Media; D018076:DNA, Complementary; D008840:Microfilament Proteins; C052523:actin filament bundling proteins