Mini-titins in striated and smooth molluscan muscles: structure, location and immunological crossreactivity.
Invertebrate mini-titins are members of a class of myosin-binding proteins belonging to the immunoglobulin superfamily that may have structural and/or regulatory properties. We have isolated mini-titins from three molluscan sources: the striated and smooth adductor muscles of the scallop, and the smooth catch muscles of the mussel. Electron microscopy reveals flexible rod-like molecules about 0.2 micron long and 30 A wide with a distinctive polarity. Antibodies to scallop mini-titin label the A-band and especially the A/I junction of scallop striated muscle myofibrils by indirect immunofluorescence and immuno-electron microscopy. This antibody crossreacts with mini-titins in scallop smooth and Mytilus catch muscles, as well as with proteins in striated muscles from Limulus, Lethocerus (asynchronous flight muscle), and crayfish. It labels the A/I junction (I-region in Lethocerus) in these striated muscles as well as in chicken skeletal muscle. Antibodies to the repetitive immunoglobulin-like regions and also to the kinase domain of nematode twitchin crossreact with scallop mini-titin and label the A-band of scallop myofibrils. Electron microscopy of single molecules shows that antibodies to twitchin kinase bind to scallop mini-titin near one end of the molecule, suggesting how the scallop structure might be aligned with the sequence of nematode twitchin.
Vibert
P
P
Rosenstiel Center, Brandeis University, Waltham, MA 02254.
Edelstein
S M
SM
Castellani
L
L
Elliott
B W
BW
D000818:Animals; D000906:Antibodies / Q000032:analysis / Q000276:immunology; D003400:Astacoidea; D015153:Blotting, Western; D029742:Caenorhabditis elegans Proteins; D002148:Calmodulin-Binding Proteins; D064211:Connectin; D003429:Cross Reactions; D005455:Fluorescent Antibody Technique; D015801:Helminth Proteins / Q000032:analysis / Q000276:immunology; D006737:Horseshoe Crabs; D007313:Insecta; D016253:Microscopy, Immunoelectron; D008974:Mollusca / Q000737:chemistry*; D009124:Muscle Proteins / Q000032:analysis / Q000737:chemistry / Q000276:immunology; D009130:Muscle, Smooth / Q000737:chemistry* / Q000502:physiology / Q000648:ultrastructure; D009132:Muscles / Q000737:chemistry* / Q000502:physiology / Q000648:ultrastructure; D011494:Protein Kinases
D000906:Antibodies; D029742:Caenorhabditis elegans Proteins; D002148:Calmodulin-Binding Proteins; D064211:Connectin; D015801:Helminth Proteins; D009124:Muscle Proteins; C489233:unc-22 protein, C elegans; D011494:Protein Kinases