Worm Breeder's Gazette 14(1): 39 (October 1, 1995)
These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
| 1 | Department of Neurology and the Verna and Marrs McLean Department of Biochemistry, Baylor of Medicine, Houston, Texas |
| 2 | The Verna and Marrs McLean Department of Biochemistry, Baylor College of Medicine, Houston, Texas |
| 3 | Department of Neurology, Baylor College of Medicine, Houston, Texas |
Understanding the structure and mechanism of assembly of thick filaments have been long-standing problems in the field of muscle biology. Cores which represent the backbones of thick filaments and consist of paramyosin and associated proteins were isolated from the nematode Caenorhabditis elegans. Electron microscopy of negative stained and frozen hydrated cores was performed. The resulting images were analyzed by computing their Fourier transforms, three-dimensional reconstruction, and by modeling. A preliminary three-dimensional model is proposed in which the paramyosin constitutes an outer sheath of seven subfilaments about a set of inner 54-nm-long tubules which repeat every 72 nm. The subfilaments are not closely packed but require cross-linking by the internal tubules. Each subfilament consist of two strands of paramyosin molecules which are staggered by 72 nm with respect to one another. This stagger introduces a 22-nm gap between consecutive paramyosin molecules in each strand. An offset of the center of the inner tubules relative to the center of the gap of 6 nm was consistent with the images and their transforms. This model suggest that the nonhelical ends of paramyosin and the unpaired gap between adjacent paramyosin molecules contain sites for the interaction with the inner tubular proteins. The molecular interactions at this locus would appear to be critical in the assembly of thick filaments and their regulation.