Abstract
Immunoelectron microscopy was used to study the nature and origin of 'gap' filaments in frog semitendinosus muscle. Gap filaments are fine longitudinal filaments observable only in sarcomeres stretched beyond thick/thin filament overlap: they occupy the gap between the tips of thick and thin filaments. To test whether the gap filaments are part of the titin-filament system, we employed monoclonal antibodies to titin (T-11, Sigma) and observed the location of the epitope at a series of sarcomere lengths. At resting sarcomere length, the epitope was positioned in the I-band approximately 50 nm beyond the apparent ends of the thick filament. The location did not change perceptibly with increasing sarcomere length up to 3.6 μm. Above 3.6 μm, the span between the epitope and the end of the A-band abruptly increased, and above 4 μm, the antibodies could be seen to decorate the gap filaments. Between 5 and 6 μm, the epitope remained approximately in the middle of the gap. Even with this high degree of stretch, the label remained more or less aligned across the myofibril. The abrupt increase of span beyond 3.6 μm implies that the A-band domain of titin is pulled free of its anchor points along the thick filament, and moves toward the gap. Although this domain is functionally inextensible at physiological sarcomere length, the epitope movement in extremely stretched muscle shows that it is intrinsically elastic. Thus, the evidence confirms that gap filaments are clearly part of the titin-filament system. They are derived not only from the I-band domain of titin, but also from its A-band domain.
| Original language | English |
|---|---|
| Pages (from-to) | 809-814 |
| Number of pages | 6 |
| Journal | Journal of Cell Science |
| Volume | 100 |
| Issue number | 4 |
| Publication status | Published - Dec 1991 |
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Keywords
- Elastic filament
- Immunoelectron microscopy
- Skeletal muscle
- Titin
ASJC Scopus subject areas
- Cell Biology
Cite this
Nature and origin of gap filaments in striated muscle. / Trombitás, K.; Baatsen, P. H W W; Kellermayer, M.; Pollack, G. H.
In: Journal of Cell Science, Vol. 100, No. 4, 12.1991, p. 809-814.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Nature and origin of gap filaments in striated muscle
AU - Trombitás, K.
AU - Baatsen, P. H W W
AU - Kellermayer, M.
AU - Pollack, G. H.
PY - 1991/12
Y1 - 1991/12
N2 - Immunoelectron microscopy was used to study the nature and origin of 'gap' filaments in frog semitendinosus muscle. Gap filaments are fine longitudinal filaments observable only in sarcomeres stretched beyond thick/thin filament overlap: they occupy the gap between the tips of thick and thin filaments. To test whether the gap filaments are part of the titin-filament system, we employed monoclonal antibodies to titin (T-11, Sigma) and observed the location of the epitope at a series of sarcomere lengths. At resting sarcomere length, the epitope was positioned in the I-band approximately 50 nm beyond the apparent ends of the thick filament. The location did not change perceptibly with increasing sarcomere length up to 3.6 μm. Above 3.6 μm, the span between the epitope and the end of the A-band abruptly increased, and above 4 μm, the antibodies could be seen to decorate the gap filaments. Between 5 and 6 μm, the epitope remained approximately in the middle of the gap. Even with this high degree of stretch, the label remained more or less aligned across the myofibril. The abrupt increase of span beyond 3.6 μm implies that the A-band domain of titin is pulled free of its anchor points along the thick filament, and moves toward the gap. Although this domain is functionally inextensible at physiological sarcomere length, the epitope movement in extremely stretched muscle shows that it is intrinsically elastic. Thus, the evidence confirms that gap filaments are clearly part of the titin-filament system. They are derived not only from the I-band domain of titin, but also from its A-band domain.
AB - Immunoelectron microscopy was used to study the nature and origin of 'gap' filaments in frog semitendinosus muscle. Gap filaments are fine longitudinal filaments observable only in sarcomeres stretched beyond thick/thin filament overlap: they occupy the gap between the tips of thick and thin filaments. To test whether the gap filaments are part of the titin-filament system, we employed monoclonal antibodies to titin (T-11, Sigma) and observed the location of the epitope at a series of sarcomere lengths. At resting sarcomere length, the epitope was positioned in the I-band approximately 50 nm beyond the apparent ends of the thick filament. The location did not change perceptibly with increasing sarcomere length up to 3.6 μm. Above 3.6 μm, the span between the epitope and the end of the A-band abruptly increased, and above 4 μm, the antibodies could be seen to decorate the gap filaments. Between 5 and 6 μm, the epitope remained approximately in the middle of the gap. Even with this high degree of stretch, the label remained more or less aligned across the myofibril. The abrupt increase of span beyond 3.6 μm implies that the A-band domain of titin is pulled free of its anchor points along the thick filament, and moves toward the gap. Although this domain is functionally inextensible at physiological sarcomere length, the epitope movement in extremely stretched muscle shows that it is intrinsically elastic. Thus, the evidence confirms that gap filaments are clearly part of the titin-filament system. They are derived not only from the I-band domain of titin, but also from its A-band domain.
KW - Elastic filament
KW - Immunoelectron microscopy
KW - Skeletal muscle
KW - Titin
UR - http://www.scopus.com/inward/record.url?scp=0026344028&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0026344028&partnerID=8YFLogxK
M3 - Article
C2 - 1726102
AN - SCOPUS:0026344028
VL - 100
SP - 809
EP - 814
JO - Journal of Cell Science
JF - Journal of Cell Science
SN - 0021-9533
IS - 4
ER -