2W4U image
Deposition Date 2008-12-02
Release Date 2010-08-25
Last Version Date 2024-05-08
Entry Detail
PDB ID:
2W4U
Title:
Isometrically contracting insect asynchronous flight muscle quick frozen after a length step
Biological Source:
Source Organism:
Method Details:
Experimental Method:
Aggregation State:
FILAMENT
Reconstruction Method:
HELICAL
Macromolecular Entities
Polymer Type:polypeptide(L)
Molecule:TROPONIN C, SKELETAL MUSCLE
Gene (Uniprot):TNNC2
Chain IDs:A (auth: 0), D (auth: 3), G (auth: 6), J (auth: 9)
Chain Length:159
Number of Molecules:4
Biological Source:GALLUS GALLUS
Polymer Type:polypeptide(L)
Molecule:TROPONIN T, FAST SKELETAL MUSCLE ISOFORMS
Gene (Uniprot):TNNT3
Chain IDs:B (auth: 1), E (auth: 4), H (auth: 7), IA (auth: Y)
Chain Length:90
Number of Molecules:4
Biological Source:GALLUS GALLUS
Polymer Type:polypeptide(L)
Molecule:TROPONIN I, FAST SKELETAL MUSCLE
Gene (Uniprot):TNNI2
Chain IDs:C (auth: 2), F (auth: 5), I (auth: 8), JA (auth: Z)
Chain Length:141
Number of Molecules:4
Biological Source:GALLUS GALLUS
Polymer Type:polypeptide(L)
Molecule:TROPOMYOSIN ALPHA-1 CHAIN
Gene (Uniprot):TPM1
Chain IDs:K (auth: A), L (auth: B), M (auth: C), DA (auth: T), EA (auth: U), FA (auth: V), GA (auth: W), HA (auth: X)
Chain Length:277
Number of Molecules:8
Biological Source:ORYCTOLAGUS CUNICULUS
Polymer Type:polypeptide(L)
Molecule:ACTIN, ALPHA SKELETAL MUSCLE
Gene (Uniprot):ACTA1
Chain IDs:N (auth: D), O (auth: E), P (auth: F), Q (auth: G), R (auth: H), S (auth: I), T (auth: J), U (auth: K), V (auth: L), W (auth: M), X (auth: N), Y (auth: O), Z (auth: P), AA (auth: Q), BA (auth: R), CA (auth: S)
Chain Length:372
Number of Molecules:16
Biological Source:ORYCTOLAGUS CUNICULUS
Ligand Molecules
Primary Citation
Structural Changes in Isometrically Contracting Insect Flight Muscle Trapped Following a Mechanical Perturbation.
Plos One 7 39422 ? (2012)
PMID: 22761792 DOI: 10.1371/JOURNAL.PONE.0039422

Abstact

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.

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