Three-dimensional structure of the basketweave Z-band in midshipman fish sonic muscle
File(s)
Accepted version
Author(s)
Type
Journal Article
Abstract
Striated muscle enables movement in all animals by the contraction of myriads of sarcomeres joined end to end by the Z-bands. The contraction is due to tension generated in each sarcomere between overlapping arrays of actin and myosin filaments. At the Z-band, actin filaments from adjoining sarcomeres overlap and are cross-linked in a regular pattern mainly by the protein α-actinin. The Z-band is dynamic, reflected by the 2 regular patterns seen in transverse section electron micrographs; the so-called small-square and basketweave forms. Although these forms are attributed, respectively, to relaxed and actively contracting muscles, the basketweave form occurs in certain relaxed muscles as in the muscle studied here. We used electron tomography and subtomogram averaging to derive the 3D structure of the Z-band in the swimbladder sonic muscle of type I male plainfin midshipman fish (Porichthys notatus), into which we docked the crystallographic structures of actin and α-actinin. The α-actinin links run diagonally between connected pairs of antiparallel actin filaments and are oriented at an angle of about 25° away from the actin filament axes. The slightly curved and flattened structure of the α-actinin rod has a distinct fit into the map. The Z-band model provides a detailed understanding of the role of α-actinin in transmitting tension between actin filaments in adjoining sarcomeres.
Date Issued
2019-07-30
Date Acceptance
2019-06-24
Citation
Proceedings of the National Academy of Sciences, 2019, 116 (31), pp.15534-15539
ISSN
0027-8424
Publisher
National Academy of Sciences
Start Page
15534
End Page
15539
Journal / Book Title
Proceedings of the National Academy of Sciences
Volume
116
Issue
31
Copyright Statement
© 2019 National Academy of Sciences. Published under the PNAS license.
Sponsor
British Heart Foundation
Identifier
https://www.pnas.org/content/early/2019/07/17/1902235116
Grant Number
RG/11/21/29335
Subjects
Science & Technology
Multidisciplinary Sciences
Science & Technology - Other Topics
Z-line
Z-disc
alpha-actinin
electron tomography
subtomogram averaging
ALPHA-ACTININ
STRIATED-MUSCLE
Z-DISK
TITIN
ULTRASTRUCTURE
VISUALIZATION
ORGANIZATION
ARCHITECTURE
SARCOMERE
SYMMETRY
Z-disc
Z-line
electron tomography
subtomogram averaging
α-actinin
Publication Status
Published
Date Publish Online
2019-07-18