[Evolution of mechanisms regulating the reaction between actin and myosin].

In the paper we consider some aspects of evolution of actin, myosin, and Ca2+-binding proteins regulating their interaction. On the basis of the data recently obtained, we propose the following theses: 1. All types of motility in the living world where actin and myosin are involved, are based on active sliding of actin filaments along myosin filaments (or less organized myosin aggregates). 2. Ca2+-sensitivity of actin-myosin interaction is as old as actin and myosin themselves. Therefore, Ca2+-independent actomyosin ATPase found in vitro does not correspond to physiological sutuation and in this sense relfects an experimental artefact. 3. All proteins which regulate Ca2+-sensitivity of actin and myosin interaction, contain EF-hand structure. 4. It is generally believed that non-muscle cells, including Protozoa and Myxomycetes, contain all regulatory mechanisms which were described for muscles. However, in our opinion, troponin complex similar to that found in striated muscles, if present does not operate there.