Show simple item record Wu, S Liu, J Reedy, MC Tregear, RT Winkler, H Franzini-Armstrong, C Sasaki, H Lucaveche, C Goldman, YE Reedy, MK Taylor, KA
dc.coverage.spatial United States 2011-06-21T17:32:14Z 2010-09-09
dc.identifier.citation PLoS One, 2010, 5 (9)
dc.description.abstract BACKGROUND: Isometric muscle contraction, where force is generated without muscle shortening, is a molecular traffic jam in which the number of actin-attached motors is maximized and all states of motor action are trapped with consequently high heterogeneity. This heterogeneity is a major limitation to deciphering myosin conformational changes in situ. METHODOLOGY: We used multivariate data analysis to group repeat segments in electron tomograms of isometrically contracting insect flight muscle, mechanically monitored, rapidly frozen, freeze substituted, and thin sectioned. Improved resolution reveals the helical arrangement of F-actin subunits in the thin filament enabling an atomic model to be built into the thin filament density independent of the myosin. Actin-myosin attachments can now be assigned as weak or strong by their motor domain orientation relative to actin. Myosin attachments were quantified everywhere along the thin filament including troponin. Strong binding myosin attachments are found on only four F-actin subunits, the "target zone", situated exactly midway between successive troponin complexes. They show an axial lever arm range of 77°/12.9 nm. The lever arm azimuthal range of strong binding attachments has a highly skewed, 127° range compared with X-ray crystallographic structures. Two types of weak actin attachments are described. One type, found exclusively in the target zone, appears to represent pre-working-stroke intermediates. The other, which contacts tropomyosin rather than actin, is positioned M-ward of the target zone, i.e. the position toward which thin filaments slide during shortening. CONCLUSION: We present a model for the weak to strong transition in the myosin ATPase cycle that incorporates azimuthal movements of the motor domain on actin. Stress/strain in the S2 domain may explain azimuthal lever arm changes in the strong binding attachments. The results support previous conclusions that the weak attachments preceding force generation are very different from strong binding attachments.
dc.language eng
dc.language.iso en_US en_US
dc.relation.ispartof PLoS One
dc.relation.isversionof 10.1371/journal.pone.0012643
dc.subject Actins
dc.subject Animals
dc.subject Cryopreservation
dc.subject Crystallography, X-Ray
dc.subject Electron Microscope Tomography
dc.subject Flight, Animal
dc.subject Insect Proteins
dc.subject Insects
dc.subject Isometric Contraction
dc.subject Models, Molecular
dc.subject Muscles
dc.subject Myosins
dc.subject Protein Binding
dc.subject Protein Structure, Tertiary
dc.subject Tissue Fixation
dc.title Electron tomography of cryofixed, isometrically contracting insect flight muscle reveals novel actin-myosin interactions.
dc.title.alternative en_US
dc.type Journal Article
dc.description.version Version of Record en_US 2010-9-9 en_US
duke.description.endpage e12643 en_US
duke.description.issue 9 en_US
duke.description.startpage e12643 en_US
duke.description.volume 5 en_US
dc.relation.journal Plos One en_US
pubs.issue 9
pubs.organisational-group /Duke
pubs.organisational-group /Duke/School of Medicine
pubs.organisational-group /Duke/School of Medicine/Basic Science Departments
pubs.organisational-group /Duke/School of Medicine/Basic Science Departments/Cell Biology
pubs.publication-status Published online
pubs.volume 5
dc.identifier.eissn 1932-6203

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