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Open AccessArticle

Different Myosin Head Conformations in Bony Fish Muscles Put into Rigor at Different Sarcomere Lengths

1
School of Medicine, Imperial College, London SW7 2AZ, UK
2
School of Optometry and Vision Science, Cardiff University, Cardiff CF19 3NB, UK
3
European Synchrotron Radiation Facility, CS 40220, 38043 Grenoble, France
4
School of Physiology, Pharmacology and Neuroscience, University of Bristol, Bristol BS8 1TD, UK
*
Author to whom correspondence should be addressed.
Present address: Genetic Microdevices Ltd., Unit 6, Princess Mews, Horace Road, Kingston-upon-Thames, Surrey KT1 2SZ, UK.
Present address: Laboratory of X-ray Engineering; Luebeck University of Applied Science, Mönkhofer Weg 239, 23562 Lübeck, Germany.
Int. J. Mol. Sci. 2018, 19(7), 2091; https://doi.org/10.3390/ijms19072091
Received: 30 June 2018 / Revised: 13 July 2018 / Accepted: 14 July 2018 / Published: 18 July 2018
(This article belongs to the Special Issue The Actin-Myosin Interaction in Muscle)
At a resting sarcomere length of approximately 2.2 µm bony fish muscles put into rigor in the presence of BDM (2,3-butanedione monoxime) to reduce rigor tension generation show the normal arrangement of myosin head interactions with actin filaments as monitored by low-angle X-ray diffraction. However, if the muscles are put into rigor using the same protocol but stretched to 2.5 µm sarcomere length, a markedly different structure is observed. The X-ray diffraction pattern is not just a weaker version of the pattern at full overlap, as might be expected, but it is quite different. It is compatible with the actin-attached myosin heads being in a different conformation on actin, with the average centre of cross-bridge mass at a higher radius than in normal rigor and the myosin lever arms conforming less to the actin filament geometry, probably pointing back to their origins on their parent myosin filaments. The possible nature of this new rigor cross-bridge conformation is discussed in terms of other well-known states such as the weak binding state and the ‘roll and lock’ mechanism; we speculate that we may have trapped most myosin heads in an early attached strong actin-binding state in the cross-bridge cycle on actin. View Full-Text
Keywords: rigor muscle; myosin cross-bridge cycle; steric blocking mechanism; roll and lock mechanism; low-angle X-ray diffraction; synchrotron radiation; bony fish muscle rigor muscle; myosin cross-bridge cycle; steric blocking mechanism; roll and lock mechanism; low-angle X-ray diffraction; synchrotron radiation; bony fish muscle
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Eakins, F.; Harford, J.J.; Knupp, C.; Roessle, M.; Squire, J.M. Different Myosin Head Conformations in Bony Fish Muscles Put into Rigor at Different Sarcomere Lengths. Int. J. Mol. Sci. 2018, 19, 2091.

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