The basic mechanism of ATP powered motor proteins

The ability of ATP powered motor proteins to convert chemical free energy into the mechanical work required to move intra-cellular organelles is discussed in terms of the molecular and dynamic fundamentals involved in producing such movements. This is carried out in detail for muscle contraction with the result that in order for a myosin head to act as a motor protein, it is necessary for it to be able to impose a unique series of impacts on an actin filament. It is further shown that these impacts can be generated when a single water molecule is transiently attached to the ADP formed during one step of an ATP cycle in the myosin head. This analysis leads to the conclusion that muscle must be a type of heat machine which has the capability of attaining mechanochemical efficiencies that approach 100%. An extension of ATP powered motor proteins in general is made with the finding that they must share the same motor mechanism of the transiently attached water molecule. A possible application of these considerations to the problem of the active transport of ions is also pointed out.