Actin as an energy transducer

Abstract

When active muscle is stretched, the energy-yielding process for contraction is reversed. In this “reversed contraction”, work is expanded to resynthesize ATP and thus in this process muscle may be classed with mitochondria and chloroplasts. It is argued that actin, the main constituent of the thin filaments, is analogous to the coupling factors of mitochondria and chloroplasts where ATP resynthesis takes place.