The myosin motor in muscle generates a smaller and slower working stroke at higher load

Massimo Reconditi, Marco Linari, Leonardo Lucii, Alex Stewart, Yin-Biao Sun, Peter Boesecke, Theyencheri Narayanan, Robert F. Fischetti, Tom Irving, Gabriella Piazzesi, Malcolm Irving and Vincenzo Lombardi ()
Additional contact information
Massimo Reconditi: DBAG, Università di Firenze
Marco Linari: DBAG, Università di Firenze
Leonardo Lucii: DBAG, Università di Firenze
Alex Stewart: Brandeis University
Yin-Biao Sun: King's College London
Peter Boesecke: European Synchrotron Radiation Facility
Theyencheri Narayanan: European Synchrotron Radiation Facility
Robert F. Fischetti: BioCAT Advanced Photon Source
Tom Irving: BioCAT Advanced Photon Source
Gabriella Piazzesi: DBAG, Università di Firenze
Malcolm Irving: King's College London
Vincenzo Lombardi: DBAG, Università di Firenze

Nature, 2004, vol. 428, issue 6982, 578-581

Abstract: Abstract Muscle contraction is driven by the motor protein myosin II, which binds transiently to an actin filament, generates a unitary filament displacement or ‘working stroke’, then detaches and repeats the cycle. The stroke size has been measured previously using isolated myosin II molecules at low load, with rather variable results1,2,3,4, but not at the higher loads that the motor works against during muscle contraction. Here we used a novel X-ray-interference technique5,6 to measure the working stroke of myosin II at constant load7 in an intact muscle cell, preserving the native structure and function of the motor. We show that the stroke is smaller and slower at higher load. The stroke size at low load is likely to be set by a structural limit8,9; at higher loads, the motor detaches from actin before reaching this limit. The load dependence of the myosin II stroke is the primary molecular determinant of the mechanical performance and efficiency of skeletal muscle.

Date: 2004
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DOI: 10.1038/nature02380

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