Credit: M. ROSENBERG/PHYSIOL. SOC. ARCHIVE

“In spite of the numerous investigations which have been made into the changes of the striations of muscle when it contracts, there is little agreement at the present day on either the nature or the significance of these changes.” Thus started the first of two independent, ground-breaking papers1,2, published together in Nature on 22 May 1954, which brought general agreement about those changes. The papers showed that muscle shortens by relative sliding between two sets of subcellular filaments containing the proteins myosin and actin. This was the first demonstration that a cell's primary function could be understood in terms of a fundamental interaction between two protein molecules.

In the first of the papers1, Andrew Huxley and Rolf Niedergerke reported measurements of the optically dense ‘A-bands’ in intact fibres from striated (skeletal) muscle. Using a novel interference microscope, the authors demonstrated that the width of the A-bands remains constant during contraction. To account for their observations, they suggested a ‘sliding-filament’ model in which myosin filaments run the length of the A-band and actin filaments slide into this band when muscle shortens.

In the second paper2, Hugh Huxley (no relation to Andrew) and Jean Hanson described their light-microscope investigations of isolated myofibrils from striated muscle; myofibrils are subfibres of muscle that are thinner and more suitable for light microscopy. Huxley and Hanson independently established the constancy of the A-band width and also invoked a sliding-filament model to explain their data. They also extracted myosin from the A-bands and demonstrated the role of ATP hydrolysis in powering the contraction–relaxation cycle of muscle.

Pictured here are the four protagonists. Clockwise from bottom left: Andrew Huxley, Rolf Niedergerke, Hugh Huxley and Jean Hanson.

The impact of the early work, and later developments in understanding the molecular mechanisms of what have since become known as motor proteins, are the subject of two meetings3,4 to be held in London next week. The two classic papers are reproduced in full in a special web focus5. The web focus also includes selected Nature publications that subsequently advanced our understanding of the molecular basis of muscle contraction and its bearing on an intriguing issue — the biological conversion of chemical energy into mechanical work.