Muscle organization in Caenorhabditis elegans: localization of proteins implicated in thin filament attachment and I-band organization.
The body wall muscle cells of Caenorhabditis elegans contain an obliquely striated myofibrillar lattice that is associated with the cell membrane through two structures: an M-line analogue in the A-band and a Z-disc analogue, or dense-body, in the I-band. By using a fraction enriched in these structures as an immunogen for hybridoma production, we prepared monoclonal antibodies that identify four components of the I-band as determined by immunofluorescence and Western transfer analysis. A major constituent of the dense-body is a 107,000-D polypeptide that shares determinants with vertebrate alpha-actinin. A second dense-body constituent is a more basic and antigenically distinct 107,000-D polypeptide that is localized to a narrow domain of the dense-body at or subjacent to the plasma membrane. This basic dense-body polypeptide is also found at certain cell boundaries where thin filaments in half-bands terminate at membrane-associated structures termed attachment plaques. A third, unidentified antigen is also found closely apposed to the cell membrane in regions of not only the dense-body and attachment plaque, but also the M-line analogue. Finally, a fourth high molecular weight antigen, composed of two polypeptides of approximately 400,000-D, is localized to the I-band regions surrounding the dense-body. The attachment of the dense-body to the cell surface and the differential localization of the dense-body-associated antigens suggest a model for their organization in which the unidentified antigen is a cell surface component, and the two 107,000-D polypeptides define different cytoplasmic domains of the dense-body.
Francis
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Waterston
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D000185:Actinin / Q000276:immunology; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D000918:Antibody Specificity; D002107:Caenorhabditis / Q000033:anatomy & histology*; D000939:Epitopes / Q000276:immunology; D005455:Fluorescent Antibody Technique; D009124:Muscle Proteins / Q000276:immunology / Q000302:isolation & purification*; D009132:Muscles / Q000032:analysis / Q000648:ultrastructure*; D010455:Peptides / Q000276:immunology; D011817:Rabbits; D012518:Sarcomeres / Q000032:analysis / Q000648:ultrastructure
D000911:Antibodies, Monoclonal; D000939:Epitopes; D009124:Muscle Proteins; D010455:Peptides; D000185:Actinin