Electron-microscopical localization of gelsolin in various crustacean muscles |
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Authors: | Andreas Unger Horst Hinssen |
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Institution: | 2. Institute of Anatomy and Cell Biology, University of Freiburg, Albertstrasse 23, 79104, Freiburg, Germany 1. Biochemical Cell Biology, Faculty of Biology, University of Bielefeld, Universit?tsstr 25, 33615, Bielefeld, Germany
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Abstract: | Gelsolin was localized by immunoelectron microscopy in fast and slow cross-striated muscles of the lobster Homarus americanus. When ultrathin sections of the muscles were labelled with anti-gelsolin and a gold-conjugated second antibody, 90% of all
gold particles in the myoplasm were detected on myofibrils, preferentially in the I-band and AI-region of the sarcomeres.
Both the region of the H-zone (lacking thin filaments) and the Z-disc contained no or little gold label. Under physiological
conditions, a close association of gelsolin with the thin filaments was observed for both muscle types. The preferential localization
of particles in the I- and AI-region indicated that gelsolin was distributed randomly over the whole length of the thin filaments.
Preincubation of muscle strips with Ringer solution containing 0.5 mM EGTA resulted in a significantly different distribution
pattern; gold particles were now localized preferentially in the cell periphery close to the sarcolemma, with significantly
decreased abundance in the centre of the cell. Compared with the muscle under physiological conditions, the number of gold
particles over sarcomeric structures was significantly reduced. Thus, binding of gelsolin to the thin filaments is apparently
reversible in vivo and depends on the presence of calcium ions. We assume a functional role for gelsolin in the actin turnover
processes in invertebrate muscle systems. |
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