RRC ID 31280
Author Arikawa M, Saito A, Omura G, Khan SM, Suetomo Y, Kakuta S, Suzaki T.
Title Ca2+-dependent in vitro contractility of a precipitate isolated from an extract of the heliozoon Actinophrys sol.
Journal Cell Motil. Cytoskeleton
Abstract Contraction of axopodia in actinophrid heliozoons (protozoa) is induced by a unique contractile structure, the "contractile tubules structure (CTS)". We have previously shown that a cell homogenate of the heliozoon Actinophrys sol yields a precipitate on addition of Ca2+ that is mainly composed of filamentous structures morphologically identical to the CTS. In this study, to further characterize the nature of the CTS in vitro, biochemical and physiological properties of the precipitate were examined. SDS-PAGE analysis showed that the Ca2+-induced precipitate was composed of many proteins, and that no proteins in the precipitate showed any detectable changes in electrophoretic mobility on addition of Ca2+. Addition of extraneous proteins such as bovine serum albumin to the cell homogenate resulted in cosedimentation of the proteins with the Ca2+-induced precipitate, suggesting that the CTS has a high affinity for other proteins that are not related to precipitate formation. Appearance and disappearance of the precipitate were repeatedly induced by alternating addition of Ca2+ and EGTA, and its protein composition remained unchanged even after repeated cycles. When adhered to a glass surface, the precipitate showed Ca2+-dependent contractility with a threshold of 10-100 nM, and this contractility was not inhibited by colchicine or cytochalasin B. The precipitate repeatedly contracted and relaxed with successive addition and removal of Ca2+, indicating that the contraction was controlled by Ca2+ alone with no need for any other energy supply. From our characterization of the precipitate, we concluded that its Ca2+-dependent formation and contraction are associated with the unique contractile organelle, the "contractile tubules structure".
Volume 63(2)
Pages 57-65
Published 2006-2
DOI 10.1002/cm.20106
PMID 16362955
MeSH Animals Calcium / metabolism* Electrophoresis, Polyacrylamide Gel Eukaryota / chemistry Eukaryota / physiology Eukaryota / ultrastructure* Immunoblotting In Vitro Techniques Organelles / chemistry Organelles / metabolism* Organelles / ultrastructure Protozoan Proteins / metabolism* Pseudopodia / chemistry Pseudopodia / metabolism* Pseudopodia / ultrastructure
Times Cited 1
WOS Category CELL BIOLOGY
Resource
Algae NIES-2497