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Structural Changes in Isometrically Contracting Insect Flight Muscle Trapped following a Mechanical Perturbation
The application of rapidly applied length steps to actively contracting muscle is a classic method for synchronizing the response of myosin cross-bridges so that the average response of the ensemble can be measured. Alternatively, electron tomography (ET) is a technique that can report the structure...
Autores principales: | , , , , , , , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
Publicado: |
Public Library of Science
2012
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3382574/ https://www.ncbi.nlm.nih.gov/pubmed/22761792 http://dx.doi.org/10.1371/journal.pone.0039422 |
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author | Wu, Shenping Liu, Jun Reedy, Mary C. Perz-Edwards, Robert J. Tregear, Richard T. Winkler, Hanspeter Franzini-Armstrong, Clara Sasaki, Hiroyuki Lucaveche, Carmen Goldman, Yale E. Reedy, Michael K. Taylor, Kenneth A. |
author_facet | Wu, Shenping Liu, Jun Reedy, Mary C. Perz-Edwards, Robert J. Tregear, Richard T. Winkler, Hanspeter Franzini-Armstrong, Clara Sasaki, Hiroyuki Lucaveche, Carmen Goldman, Yale E. Reedy, Michael K. Taylor, Kenneth A. |
author_sort | Wu, Shenping |
collection | PubMed |
description | The application of rapidly applied length steps to actively contracting muscle is a classic method for synchronizing the response of myosin cross-bridges so that the average response of the ensemble can be measured. Alternatively, electron tomography (ET) is a technique that can report the structure of the individual members of the ensemble. We probed the structure of active myosin motors (cross-bridges) by applying 0.5% changes in length (either a stretch or a release) within 2 ms to isometrically contracting insect flight muscle (IFM) fibers followed after 5–6 ms by rapid freezing against a liquid helium cooled copper mirror. ET of freeze-substituted fibers, embedded and thin-sectioned, provides 3-D cross-bridge images, sorted by multivariate data analysis into ∼40 classes, distinct in average structure, population size and lattice distribution. Individual actin subunits are resolved facilitating quasi-atomic modeling of each class average to determine its binding strength (weak or strong) to actin. ∼98% of strong-binding acto-myosin attachments present after a length perturbation are confined to “target zones” of only two actin subunits located exactly midway between successive troponin complexes along each long-pitch helical repeat of actin. Significant changes in the types, distribution and structure of actin-myosin attachments occurred in a manner consistent with the mechanical transients. Most dramatic is near disappearance, after either length perturbation, of a class of weak-binding cross-bridges, attached within the target zone, that are highly likely to be precursors of strong-binding cross-bridges. These weak-binding cross-bridges were originally observed in isometrically contracting IFM. Their disappearance following a quick stretch or release can be explained by a recent kinetic model for muscle contraction, as behaviour consistent with their identification as precursors of strong-binding cross-bridges. The results provide a detailed model for contraction in IFM that may be applicable to contraction in other types of muscle. |
format | Online Article Text |
id | pubmed-3382574 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2012 |
publisher | Public Library of Science |
record_format | MEDLINE/PubMed |
spelling | pubmed-33825742012-07-03 Structural Changes in Isometrically Contracting Insect Flight Muscle Trapped following a Mechanical Perturbation Wu, Shenping Liu, Jun Reedy, Mary C. Perz-Edwards, Robert J. Tregear, Richard T. Winkler, Hanspeter Franzini-Armstrong, Clara Sasaki, Hiroyuki Lucaveche, Carmen Goldman, Yale E. Reedy, Michael K. Taylor, Kenneth A. PLoS One Research Article The application of rapidly applied length steps to actively contracting muscle is a classic method for synchronizing the response of myosin cross-bridges so that the average response of the ensemble can be measured. Alternatively, electron tomography (ET) is a technique that can report the structure of the individual members of the ensemble. We probed the structure of active myosin motors (cross-bridges) by applying 0.5% changes in length (either a stretch or a release) within 2 ms to isometrically contracting insect flight muscle (IFM) fibers followed after 5–6 ms by rapid freezing against a liquid helium cooled copper mirror. ET of freeze-substituted fibers, embedded and thin-sectioned, provides 3-D cross-bridge images, sorted by multivariate data analysis into ∼40 classes, distinct in average structure, population size and lattice distribution. Individual actin subunits are resolved facilitating quasi-atomic modeling of each class average to determine its binding strength (weak or strong) to actin. ∼98% of strong-binding acto-myosin attachments present after a length perturbation are confined to “target zones” of only two actin subunits located exactly midway between successive troponin complexes along each long-pitch helical repeat of actin. Significant changes in the types, distribution and structure of actin-myosin attachments occurred in a manner consistent with the mechanical transients. Most dramatic is near disappearance, after either length perturbation, of a class of weak-binding cross-bridges, attached within the target zone, that are highly likely to be precursors of strong-binding cross-bridges. These weak-binding cross-bridges were originally observed in isometrically contracting IFM. Their disappearance following a quick stretch or release can be explained by a recent kinetic model for muscle contraction, as behaviour consistent with their identification as precursors of strong-binding cross-bridges. The results provide a detailed model for contraction in IFM that may be applicable to contraction in other types of muscle. Public Library of Science 2012-06-25 /pmc/articles/PMC3382574/ /pubmed/22761792 http://dx.doi.org/10.1371/journal.pone.0039422 Text en Wu et al. http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited. |
spellingShingle | Research Article Wu, Shenping Liu, Jun Reedy, Mary C. Perz-Edwards, Robert J. Tregear, Richard T. Winkler, Hanspeter Franzini-Armstrong, Clara Sasaki, Hiroyuki Lucaveche, Carmen Goldman, Yale E. Reedy, Michael K. Taylor, Kenneth A. Structural Changes in Isometrically Contracting Insect Flight Muscle Trapped following a Mechanical Perturbation |
title | Structural Changes in Isometrically Contracting Insect Flight Muscle Trapped following a Mechanical Perturbation |
title_full | Structural Changes in Isometrically Contracting Insect Flight Muscle Trapped following a Mechanical Perturbation |
title_fullStr | Structural Changes in Isometrically Contracting Insect Flight Muscle Trapped following a Mechanical Perturbation |
title_full_unstemmed | Structural Changes in Isometrically Contracting Insect Flight Muscle Trapped following a Mechanical Perturbation |
title_short | Structural Changes in Isometrically Contracting Insect Flight Muscle Trapped following a Mechanical Perturbation |
title_sort | structural changes in isometrically contracting insect flight muscle trapped following a mechanical perturbation |
topic | Research Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3382574/ https://www.ncbi.nlm.nih.gov/pubmed/22761792 http://dx.doi.org/10.1371/journal.pone.0039422 |
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