2W4U

Isometrically contracting insect asynchronous flight muscle quick frozen after a length step

Summary for 2W4U

• Entry DOI: 10.2210/pdb2w4u/pdb
• Related: 1ALM 1ATN 1AVS 1BLQ 1EQY 1EW7 1IJJ 1J6Z 1JC2 1KXP 1LCU 1M8Q 1MA9 1MVW 1NCX 1NCY 1NCZ 1NPQ 1NWK 1O18 1O19 1O1A 1O1B 1O1C 1O1D 1O1E 1O1F 1O1G 1P8Z 1PON 1QZ5 1QZ6 1RDW 1RFQ 1RGI 1S22 1SMG 1SQK 1T44 1TNP 1TNQ 1TNW 1TNX 1TOP 1UY5 1VDI 1WUA 1Y64 1YTZ 1ZAC 2A40 2A42 2A5X 2ASO 2ASP 2D1K 2D3E 2FF3 2FF6 2FXU 2TMA 2V51 2V52 2VCP
• EMDB information: 1584 1585
• Descriptor: TROPONIN C, SKELETAL MUSCLE, TROPONIN T, FAST SKELETAL MUSCLE ISOFORMS, TROPONIN I, FAST SKELETAL MUSCLE, ... (5 entities in total)
• Functional Keywords: contractile protein, methylation, atp-binding, isometric contraction, microtomy, freeze substitution, muscle protein, calmodulin-binding, motor protein, actin-binding
• Biological source: GALLUS GALLUS (CHICKEN); More
• Total number of polymer chains: 36
• Total formula weight: 1100083.84

Authors

Wu, S.,Liu, J.,Reedy, M.C.,Tregear, R.T.,Winkler, H.,Franzini-Armstrong, C.,Sasaki, H.,Lucaveche, C.,Goldman, Y.E.,Reedy, M.K.,Taylor, K.A. (deposition date: 2008-12-02, release date: 2010-08-25, Last modification date: 2024-05-08)

Primary citation

Wu, S.,Liu, J.,Reedy, M.C.,Perz-Edwards, R.J.,Tregear, R.T.,Winkler, H.,Franzini-Armstrong, C.,Sasaki, H.,Lucaveche, C.,Goldman, Y.E.,Reedy, M.K.,Taylor, K.A.
Structural Changes in Isometrically Contracting Insect Flight Muscle Trapped Following a Mechanical Perturbation.
Plos One, 7:39422-, 2012

PubMed Abstract: 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.

PubMed: 22761792
DOI: 10.1371/JOURNAL.PONE.0039422

Experimental method

ELECTRON MICROSCOPY (35 Å)