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Two ground-breaking papers published back-to-back in Nature 50 years ago this month, independently showed that muscle shortens as a result of the sliding between two sets of filaments containing the proteins myosin and actin (click here to see sliding in action). In this special focus, we celebrate Nature's publication of the two classic papers, giving a decade-by-decade snapshot from Nature's rich archive of subsequent publications on muscle crossbridges. These papers uncover a fascinating story of one of the most intriguing of biological problems: that of the conversion of chemical energy to mechanical work. |
 <!-- start of 50 years ago section -->  Structural changes in muscle during contraction: interference microscopy of living muscle fibres Huxley, A. F. & Niedergerke, R. Nature 173, 971-973 (22 May 1954)  Interference microscopy shows that the width of 'A bands' in muscle fibres remains constant during contraction (see picture), suggesting a 'sliding filament' model in which myosin filaments run the length of the A band and actin filaments slide into the A band.
Changes in the cross-striations of muscle during contraction and stretch and their structural interpretation Huxley, H. E., Hanson, J. Nature 173, 973-976 (22 May 1954) Light microscopy of isolated myofibrils independently establishes the sliding filament mechanism and constancy of the A-band width. Myosin is extracted from the A bands and the role of ATP hydrolysis in the contraction cycle demonstrated.
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<!-- 1960's starts ghere-->1960s Induced changes in orientation of the cross-bridges of glycerinated insect flight muscle Reedy M. K., Holmes K. C. & Tregear R. T. Nature 207(3), 1276-80-976 (18 Sep 1965) X-ray diffraction and electron microscopy demonstrate that the transition from relaxed to 'rigor' (high tension) insect flight muscle is accompanied by a re-orientation of the crossbridges between actin and myosin filaments.
<!-- start of 1970's-->1970s Proposed mechanism of force generation in striated muscle Huxley, A. F. & Simmons, R. M. Nature 233, 533-538 (22 Sep 1971) After a small rapid shortening is imposed on intact muscle fibres, the fibres quickly recover but only over a range of sliding of 10 nanometres between the myosin and actin filaments, leading to the concept of a 'working stroke' of 10 nm.
<!-- start of 1980's-->1980s Myosin subfragment-1 is sufficient to move actin filaments in vitro Toyoshima, Y. Y. et al. Nature 328, 536-539 (6 Aug 1987) Single myosin heads cause sliding of isolated actin filaments in the presence of ATP—the first direct demonstration that the 'head' of the myosin filament is the functional motor.
<!-- start of 1990's-->1990s Single myosin molecule mechanics: piconewton force and nanometre stepsFiner, J. T., Simmons, R. M. & Spudich, J. A. Nature 368, 113-119 (10 March 1994) The first direct measurement of the working stroke produced by a single myosin molecule shows excellent agreement with the 1971 measurements by Huxley and Simmons in intact muscle.
<!-- start of 1990's-->2000s The myosin motor in muscle generates a smaller and slower working stroke at higher loadM. Reconditi et al. Nature 428, 578-581 (1 Apr 2004) X-ray interference shows that the working stroke of the myosin head depends on the load of the motor.
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