Dependency of Cytoplasmic Streaming on Intracellular ATP and Mg<SUP>2+</SUP> Concentrations

Abstract

ABSTRACT.The rate of cytoplasmic streaming (v) The motive force of cytoplasmic streaming in Characeae cells is generated at the boundary between the stationary cortical gel layer and the mobile sol endoplasm (the sol-gel interface). The nature of the motive force is a shearing force produced by the organized gel surface and the sol phase (6). Bundles of microfilaments situated at the surface of the gel phase are assumed to be the component responsible for the generation of the motive force (4,5,12). The filament binds rabbit muscle heavy meromyosin in arrowhead arrays, which indicates that the filaments are F-actin (14,15,23). The relationship between the direction of the arrowheads and that of cytoplasmic streaming has also been clarified (9). Chen and Kamiya (2), and Kuroda and Kamiya (11) showed evidence suggesting that another (putative) component, myosin, is localized in the sol layer. Kato and Tonomura (8) purified myosin from Nitella flexillis.The so-called cell model is a suitable system for determining the mechanism of cell motility ; including muscle contraction (19), flagella and cilia movements (1, 13), amoeboid movement (18), movement of myxomycete plasmodium (7) and egg cleavage (10). Williamson (24) removed tonoplasts by perfusing the vacuole rapidly with a medium containing EGTA, a Ca2+-chelator. Tazawa, Kikuyama and Shimmen (21)

The sliding theory of cytoplasmic streaming: fifty years of progress

“…The ATP-dependent movement of organelles along actin bundles was directly demonstrated in tonoplast-free cells (Williamson 1975;Tazawa et al 1976). Shimmen (1978) showed the hyperbolic relation between ATP concentration and the velocity. He also showed that ADP, orthophosphate, and pyrophosphate inhibited cytoplasmic streaming by competition with ATP, but AMP did not (Shimmen 1988a).…”

III-5 Cytoplasmic Streaming

“…Cell Sci. 17, 665, 1975), higher concentrations of Ca2+ are inhibitory (Tazawa, Kikuyama and Shimmen, 1976;Shimmen, 1978 ;Hayama, Shimmen and Tazawa, 1979;Hayama and Tazawa, 1980;Kikuyama and Tazawa, 1982;Tominaga, Shimmen and Tazawa, 1983). This is also the case in movement in the myxomycete plasmodium (Yoshimoto, Matsumura and Kamiya, 1981).…”

“…With tonoplast-free internodal cells of Nitella and Chara, Shimmen (1978) showed that the ATP concentration for half saturation of the streaming rate was 0.08 mM in Nitella axillaris and 0.06 mM in Chara corallina. Mg2+ was essential at a concentration equal to, or higher than, that of ATP.…”

Effects of exogenous proteins on cytoplasmic streaming in perfused Chara cells.

“…Since TPF contains only 1 mM ATP, it seemed possible that this inhibition of streaming could have developed because all the ATP had been hydrolyzed by the added enzyme . To mg-' (29) and a HMM concentration of 0.5 mg/ml, then the time required to reduce the ATP concentration from 10 mM to 0 .3 mM (0.3 mM being saturating for streaming [43]) would be -24 min. In perfused Chara cells, however, the only actin available for HMM activation is in the endoplasm-ectoplasm region near the cell periphery.…”