Related Experiment Videos
Thick filament substructures in Caenorhabditis elegans: evidence for two populations of paramyosin
1Verna and Marrs McLean Department of Biochemistry, Baylor College of Medicine, Houston, Texas 77030.
Abstract:
The thick filaments of the nematode Caenorhabditis elegans contain two myosin heavy chain isoforms A and B and paramyosin, the products of the myo-3, unc-54, and unc-15 genes, respectively. Dissociation of paramyosin from native thick filaments at pH 6.36 shows a biphasic function with respect to NaCl concentration. Electron microscopy of the remaining structures shows 15-nm core structures that label with monoclonal anti-paramyosin antibody at 72.5-nm intervals. Purified core structures also show 72.5 nm repeats by negative staining. Structural analysis of native thick filaments and dissociated structures suggests that the more dissociable paramyosin is removed radially as well as processively from the filament ends. Minor proteins with masses of 20, 28, and 30 kD cosediment stoichiometrically with paramyosin in purified core structures.
Insights
Paramyosin, a key protein in nematode thick filaments, dissociates in a biphasic manner. This dissociation reveals core structures with repeating paramyosin antibody labels, indicating radial and processive removal.
Area of Science:
- Muscle biology
- Biochemistry
- Molecular genetics
Background:
- Thick filaments in Caenorhabditis elegans are composed of myosin heavy chain isoforms A and B, and paramyosin.
- These components are encoded by the myo-3, unc-54, and unc-15 genes.
Purpose of the Study:
- To investigate the dissociation properties of paramyosin from native thick filaments.
- To characterize the structural organization of the remaining filament core structures.
Main Methods:
- Dissociation of paramyosin from thick filaments at a specific pH (6.36) and varying NaCl concentrations.
- Electron microscopy and negative staining for structural analysis.
- Immunolabeling with monoclonal anti-paramyosin antibody.
Main Results:
- Paramyosin dissociation exhibited a biphasic relationship with NaCl concentration.
- Electron microscopy revealed 15-nm core structures with periodic labeling (72.5 nm) by anti-paramyosin antibody.
- Purified core structures also displayed 72.5 nm repeats.
- Minor proteins (20, 28, 30 kD) were found to cosediment with paramyosin in the core structures.
Conclusions:
- Paramyosin is removed radially and processively from the ends of thick filaments.
- The findings elucidate the structural organization and dissociation dynamics of paramyosin within nematode thick filaments.