Ultrastructural analysis of the dynactin complex: an actin-related protein is a component of a filament that resembles F-actin.
The dynactin complex visualized by deepetch electron microscopy appears as a short filament 37-nm in length, which resembles F-actin, plus a thinner, laterally oriented filament that terminates in two globular heads. The locations of several of the constituent polypeptides were identified on this structure by applying antibodies to decorate the dynactin complex before processing for electron microscopy. Antibodies to the actin-related protein Arp1 (previously referred to as actin-RPV), bound at various sites along the filament, demonstrating that this protein assembles in a polymer similar to conventional actin. Antibodies to the barbed-end actin-binding protein, capping protein, bound to one end of the filament. Thus, an actin-binding protein that binds conventional actin may also bind to Arp1 to regulate its polymerization. Antibodies to the 62-kD component of the dynactin complex also bound to one end of the filament. An antibody that binds the COOH-terminal region of the 160/150-kD dynactin polypeptides bound to the globular domains at the end of the thin lateral filament, suggesting that the dynactin polypeptide comprises at least part of the sidearm structure.
Schafer
D A
DA
Department of Biology, Johns Hopkins University, Baltimore, Maryland 21218.
Gill
S R
SR
Cooper
J A
JA
Heuser
J E
JE
Schroer
T A
TA
D008841:Actin Cytoskeleton / Q000737:chemistry*; D000199:Actins / Q000032:analysis / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal; D000918:Antibody Specificity; D000937:Antigen-Antibody Reactions; D001923:Brain Chemistry; D051347:CapZ Actin Capping Protein; D002642:Chick Embryo; D000072159:Dynactin Complex; D004398:Dyneins / Q000302:isolation & purification / Q000378:metabolism; D000939:Epitopes; D007526:Isoelectric Point; D008840:Microfilament Proteins; D008868:Microtubule Proteins / Q000737:chemistry / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism* / Q000648:ultrastructure*; D008869:Microtubule-Associated Proteins; D008954:Models, Biological; D008969:Molecular Sequence Data; D008970:Molecular Weight; D009124:Muscle Proteins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D009132:Muscles / Q000737:chemistry; D017421:Sequence Analysis
D000199:Actins; D000911:Antibodies, Monoclonal; D051347:CapZ Actin Capping Protein; D000072159:Dynactin Complex; D000939:Epitopes; D008840:Microfilament Proteins; D008868:Microtubule Proteins; D008869:Microtubule-Associated Proteins; D009124:Muscle Proteins; C076834:centractin; D004398:Dyneins