[Synchronous (synphaseous) additive models for mitochondrial ATP synthetase complex and for other energy transducing systems of cells (a hypothesis)].
There exist some energy transducing enzymes containing immobile molecules of substrates which are not exchangeable during protein functioning. According to the proposed models the immobile substrates are localized at the "idle" (or "partial" or "imitational") catalytic sites, which differ from normal ("working") active sites of enzymes. Only some steps of a complete reaction sequence which take place at the "working" sites are carried out at the "idle" sites. On the other hand, cyclic conversion of the immobile substrate at an "idle" catalytic site may include some steps which are absent in the "working" site cycle. The occurrence of identical steps on the "idle" and "working" catalytic sites allows to synchronize their action through conformational interconversions of tightly packed and structurally related "idle" and "working" subunits of the enzyme. The presence of covaletly bound substrates or substrates localized in closed cavities of the "idle" sites allows to synchronize the action of many monomers containing such sites due to the absence of the rate-limiting step of simultaneous saturation of many catalytic sites by substrate molecules from solution, and due to the lack of substrate inhibition on the "idle" sites. The functions of the "idle" sites are miscellaneous e.g. in ion-transporting systems these sites are directly involved in ion translocation. In the actomyosin complex the "idle" sites imitate conformational alterations of "working" sites, thus allowing synchronous functioning of the polymeric structure. Variations in the number of the "idle" sites operating simultaneously with one "working" site allow to regulate some parameters of enzymatic processes, e.g. the stoichiometry (number of transported ions per ATP hydrolysed (or synthesised) or electron-transported, or hv-absorbed ones) for ion transported systems or the ratio (velocity of contraction to developed efforts) for the actomyosin complex.
D025181:ATP Synthetase Complexes; D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D004734:Energy Metabolism; D008928:Mitochondria / Q000201:enzymology*; D008954:Models, Biological; D009097:Multienzyme Complexes / Q000378:metabolism*; D010770:Phosphotransferases / Q000378:metabolism*
D009097:Multienzyme Complexes; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D010770:Phosphotransferases; D025181:ATP Synthetase Complexes
Sinkhronnye (sinfaznye) additivnye modeli funktsionirovaniia ATP-sintetaznogo kompleksa mitokhondriĭ i drugikh énergoprevrashchaiushchikh sistem kletki (sipoteza).