Purification of an ATP-dependent actin-binding protein from a lower eukaryote, Physarum polycephalum.
ABSTRACT A novel protein with a molecular mass of 55 kDa, as determined by SDS-PAGE, was purified from plasmodia of Physarum polycephalum. The protein bound to actin filaments with a stoichiometry of 0.27 moles per mole of actin with an apparent dissociation constant of 4 x 10(-8) M. In the presence of ATP, the protein dissociated from actin filaments. Adenosine 5-(gamma-thio)triphosphate and adenyl-5'-yl imidodiphosphate also abolished the actin-binding activity of the protein, but GTP did not. Because the cytoplasmic concentration of ATP oscillates in association with the shuttle streaming of the cytoplasm, it is possible that this protein might be involved in the actin-linked regulation of cytoplasmic streaming.
- SourceAvailable from: Michihito Katayama[Show abstract] [Hide abstract]
ABSTRACT: Drebrin is a well-known side-binding protein of F-actin in the brain. Immunohistochemical data suggest that the peripheral parts of growing axons are enriched in the drebrin E isoform and mature axons are not. It has also been observed that drebrin E is concentrated in the growth cones of PC12 cells. These data strongly suggest that drebrin E plays a role in axonal growth during development. In this study, we used primary hippocampal neuronal cultures to analyze the role of drebrin E. Immunocytochemistry showed that within axonal growth cones drebrin E specifically localized to the transitional zone, an area in which dense networks of F-actins and microtubules overlapped. Over-expression of drebrin E caused drebrin E and F-actin to accumulate throughout the growth cone and facilitated axonal growth. In contrast, knockdown of drebrin E reduced drebrin E and F-actin in the growth cone and prevented axonal growth. Furthermore, inhibition of myosin II ATPase masked the promoting effects of drebrin E over-expression on axonal growth. These results suggest that drebrin E plays a role in axonal growth through actin-myosin interactions in the transitional zone of axonal growth cones.Journal of Neurochemistry 03/2009; 109(2):611-22. · 3.97 Impact Factor
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ABSTRACT: Coronin cDNA was cloned from the plasmodia of Physarum polycephalum. The amino acid sequence deduced from the cDNA was comprised of 449 residues and showed 60% identity to that of Dictyostelium discoideum coronin. Southern blot analysis suggested that the coronin gene present in the P. polycephalum genome might be a single copy. Coronin was expressed in diploid plasmodia, while it was not detected in haploid amoebae or spores.Bioscience Biotechnology and Biochemistry 04/2009; 73(3):747-9. · 1.27 Impact Factor
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ABSTRACT: We measured seasonal variations in soil CH4 uptake and CO2 emission for three consecutive years in a cool-temperate, deciduous forest in Japan. The fluxes were measured by the static closed-chamber technique during the growing season and by the gas concentration-gradient technique during winter under snow cover. The measured rates of CH4 uptake and CO2 emission showed marked seasonal variations that were correlated with soil temperatures rather than with volumetric soil water content. The Q10 (10–20°C) value of the CH4 uptake rates was 1.7, which is higher than that of other temperate forests, and that of the CO2 emission rates was 3.4 and 4.4 for soil temperatures at 0 and 5cm depths, respectively. No significant relationship was found between soil moisture and rates of CH4 uptake or CO2 emission because of the narrow range of the measured soil water content (15–31% v/v). From June 2002 to May 2003, the estimated annual CH4 uptake and CO2 emission were 1.53 and 451gCy–1, respectively. When compared with CH4 uptake rates of temperate deciduous forests worldwide (n=17), CH4 uptake rates by Japanese deciduous forest soils are at the high end of the range of reported values. This Japanese temperate forest soil is a strong CH4 sink. CH4 oxidation by methanotrophs accounted for 0.4% of the annual soil CO2 emission. The fluxes through the snowpack composed 14% of the annual CH4 uptake and 11% of the annual CO2 emission.