Active streaming against gravity in glass microcapillaries of solutions containing acto-heavy meromyosin and native tropomyosin.

Solutions containing heavy meromyosin, actin, native tropomyosin, and Mg-ATP exhibited streaming in horizontally placed glass microcapillaries. Up-hill streaming could also be observed when the capillaries were at an inclined position; this served for the clear distinction between active and passive streaming provided surface tension effects were eliminated. The presence of native tropomyosin and actin-activation of the ATPase activity of HMM were essential for the reconstitution of active streaming. The significance of the results for cytoplasmic streaming and muscle contraction is discussed.