Submicromolar concentrations of cytochalasin inhibit the rate of assembly of highly purified dictyostelium discoideum actin, using a cytochalasin concentration range in which the final extent of assembly is minimally affected. Cytochalasin D is a more effective inhibitor than cytochalasin B, which is in keeping with the effects that have been reported on cell motility and with binding to a class of high-affinity binding sites from human erythrocyte membranes (Lin and Lin. 1978. J. Biol. CHem. 253:1415; Lin and Lin. 1979. Proc. Natl. Acad. Sci. U.S.A. 76:2345); 5x10(-7) M cytochalasin B lowers it to 70 percent of the control value, whereas 10(-7) M cytochalasin B lowers the rate to 25 percent. Fragments of F-actin were used to increase the rate of assembly fivefold by providing more filament ends on to which monomers could add. Under these conditions, cytochalasin has an even more dramatic effect on the assembly rate; the concentrations of cytochalasin B and cytochalasin D required for half-maximal inhibition are 2x10(-7) M and 10(-8) M, respectively. The assembly rate is most sensitive to cytochalasin when actin assembly is carried out in the absence of ATP (with 3 mM ADP present to stabilize the actin). In this case, the concentrations of cytochalasin B and cytochalasin D required for half-maximal inhibition are 4x10(-8) M and 1x10(-9) M, respectively. A scatchard plot has been obtained using [(3)H]cytochalasin B binding to F-actin in the absence of ATP. The K(d) from this plot (approximately 4x10(-8) M) agrees well with the concentration of cytochalasin B required for half-maximal inhibition of the rate of assembly under these conditions. The number of cytochalasin binding sites is roughly one per F-actin filament, suggesting that cytochalasin has a specific action on actin filament ends.
Cytochalasin inhibits the rate of elongation of actin filament fragments
Published 1979 in Journal of Cell Biology
ABSTRACT
PUBLICATION RECORD
- Publication year
1979
- Venue
Journal of Cell Biology
- Publication date
1979-12-01
- Fields of study
Biology, Medicine, Chemistry
- Identifiers
- External record
- Source metadata
Semantic Scholar, PubMed
CITATION MAP
EXTRACTION MAP
CLAIMS
CONCEPTS
- actin assembly
The polymerization of highly purified Dictyostelium discoideum actin into filaments under the assay conditions used in the abstract.
Aliases: actin filament assembly
- actin filament ends
The terminal sites of actin filaments where monomers can add during elongation.
Aliases: filament ends
- atp-free adp-stabilized conditions
An assay condition in which ATP is absent and ADP is present to stabilize actin during assembly measurements.
Aliases: absence of ATP with 3 mM ADP, ADP-stabilized conditions
- cytochalasin b
A cytochalasin analog used here as a test inhibitor of actin filament assembly and ligand for binding measurements.
Aliases: CB
- cytochalasin d
A cytochalasin analog used here as a test inhibitor of actin filament assembly.
Aliases: CD
- f-actin fragments
Preformed fragments of filamentous actin added to the assay to provide additional elongating filament ends.
Aliases: fragmented F-actin, F-actin seeds
- scatchard plot
A binding-analysis plot used to estimate ligand affinity and binding-site number from radiolabeled binding data.
REFERENCES
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