Mini-titins in striated and smooth molluscan muscles: structure, location and immunological crossreactivity

J Muscle Res Cell Motil. 1993 Dec;14(6):598-607. doi: 10.1007/BF00141557.


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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Antibodies / analysis
  • Antibodies / immunology
  • Astacoidea
  • Blotting, Western
  • Caenorhabditis elegans Proteins
  • Calmodulin-Binding Proteins*
  • Connectin
  • Cross Reactions
  • Fluorescent Antibody Technique
  • Helminth Proteins / analysis
  • Helminth Proteins / immunology
  • Horseshoe Crabs
  • Insecta
  • Microscopy, Immunoelectron
  • Mollusca / chemistry*
  • Muscle Proteins* / analysis
  • Muscle Proteins* / chemistry
  • Muscle Proteins* / immunology
  • Muscle, Smooth / chemistry*
  • Muscle, Smooth / physiology
  • Muscle, Smooth / ultrastructure
  • Muscles / chemistry*
  • Muscles / physiology
  • Muscles / ultrastructure
  • Protein Kinases*


  • Antibodies
  • Caenorhabditis elegans Proteins
  • Calmodulin-Binding Proteins
  • Connectin
  • Helminth Proteins
  • Muscle Proteins
  • unc-22 protein, C elegans
  • Protein Kinases