title: Substructure of sea urchin egg cytoplasmic dynein.
abstract: The substructure of the cytoplasmic dynein molecule was studied using the quick-freeze, deep-etch technique. Cytoplasmic dynein purified as a 12 S form from the eggs of the sea urchin Hemicentrotus pulcherrimus was composed of a single high molecular weight polypeptide. Rotary shadowing images of cytoplasmic dynein either sprayed on to a mica surface or quick-frozen on mica flakes demonstrated a single-headed molecule, in contrast to the two-headed molecule of sea urchin sperm flagellar 21 S dynein. More detailed substructure was visualized by rotary shadowing after quick-freeze deep-etching. Cytoplasmic dynein consisted of a head and a stem. The head was pear-shaped (16 nm X 11 nm) and a little smaller than the pear-shaped head of 21 S dynein (18 nm X 14 nm). The form of the stem was irregular, and its apparent length varied from 0 to 32 nm. Binding of cytoplasmic dynein to brain microtubule in the solution was observed by negative staining, and that in the precipitate was examined by the quick-freeze, deep-etch method as well. Both methods revealed the presence of two kinds of microtubules, one a fully decorated microtubule and the other a non-decorated microtubule. Cytoplasmic dynein bound to microtubule also appeared as a globular particle. Neither the periodic binding nor the crossbridges that were observed with 21 S dynein were formed by cytoplasmic dynein, although cytoplasmic dynein appeared to bind to microtubules co-operatively.
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D000818:Animals; D003593:Cytoplasm / Q000378:metabolism / Q000648:ultrastructure; D004398:Dyneins / Q000378:metabolism; D005407:Flagella / Q000648:ultrastructure; D008854:Microscopy, Electron; D008870:Microtubules / Q000378:metabolism; D010063:Ovum / Q000648:ultrastructure*; D012617:Sea Urchins
chemical_list: D000251:Adenosine Triphosphatases; D004398:Dyneins