UNC-98 and UNC-96 interact with paramyosin to promote its incorporation into thick filaments of Caenorhabditis elegans.
Mutations in unc-96 or -98 cause reduced motility and a characteristic defect in muscle structure: by polarized light microscopy birefringent needles are found at the ends of muscle cells. Anti-paramyosin stains the needles in unc-96 and -98 mutant muscle. However there is no difference in the overall level of paramyosin in wild-type, unc-96, and -98 animals. Anti-UNC-98 and anti-paramyosin colocalize in the paramyosin accumulations of missense alleles of unc-15 (encodes paramyosin). Anti-UNC-96 and anti-UNC-98 have diffuse localization within muscles of unc-15 null mutants. By immunoblot, in the absence of paramyosin, UNC-98 is diminished, whereas in paramyosin missense mutants, UNC-98 is increased. unc-98 and -15 or unc-96 and -15 interact genetically either as double heterozygotes or as double homozygotes. By yeast two-hybrid assay and ELISAs using purified proteins, UNC-98 interacts with paramyosin residues 31-693, whereas UNC-96 interacts with a separate region of paramyosin, residues 699-798. The importance of surface charge of this 99 residue region for UNC-96 binding was shown. Paramyosin lacking the C-terminal UNC-96 binding region fails to localize throughout A-bands. We propose a model in which UNC-98 and -96 may act as chaperones to promote the incorporation of paramyosin into thick filaments.
Miller
Rachel K
RK
Department of Pathology, Graduate Division of Biological and Biomedical Sciences, and BIMCORE (Molecular Graphics), Emory University, Atlanta, GA 30322, USA.
Qadota
Hiroshi
H
Mercer
Kristina B
KB
Gernert
Kim M
KM
Benian
Guy M
GM
D000818:Animals; D030801:Animals, Genetically Modified; D001483:Base Sequence; D017173:Caenorhabditis elegans / Q000235:genetics / Q000378:metabolism*; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D003599:Cytoskeleton / Q000378:metabolism; D018509:DNA, Helminth / Q000235:genetics; D017238:Genes, Helminth; D008954:Models, Biological; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D020125:Mutation, Missense; D011485:Protein Binding; D025941:Protein Interaction Mapping; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D014335:Tropomyosin / Q000235:genetics / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D018509:DNA, Helminth; D009124:Muscle Proteins; D011994:Recombinant Proteins; D014335:Tropomyosin; C509308:UNC-15 protein, C elegans; C514106:UNC-96 protein, C elegans; C481656:UNC-98 protein, C elegans