UMMS Affiliation

Department of Cell Biology

Publication Date

1988-07-01

Document Type

Article

Subjects

Actins; Cell Membrane; Cross-Linking Reagents; Dictyostelium; Microfilaments; Models, Biological; Polymers

Disciplines

Cell Biology | Life Sciences | Medicine and Health Sciences

Abstract

We have shown previously (Schwartz, M. A., and E. J. Luna. 1986. J. Cell Biol. 102: 2067-2075) that actin binds with positive cooperativity to plasma membranes from Dictyostelium discoideum. Actin is polymerized at the membrane surface even at concentrations well below the critical concentration for polymerization in solution. Low salt buffer that blocks actin polymerization in solution also prevents actin binding to membranes. To further explore the relationship between actin polymerization and binding to membranes, we prepared four chemically modified actins that appear to be incapable of polymerizing in solution. Three of these derivatives also lost their ability to bind to membranes. The fourth derivative (EF actin), in which histidine-40 is labeled with ethoxyformic anhydride, binds to membranes with reduced affinity. Binding curves exhibit positive cooperativity, and cross-linking experiments show that membrane-bound actin is multimeric. Thus, binding and polymerization are tightly coupled, and the ability of these membranes to polymerize actin is dramatically demonstrated. EF actin coassembles weakly with untreated actin in solution, but coassembles well on membranes. Binding by untreated actin and EF actin are mutually competitive, indicating that they bind to the same membrane sites. Hill plots indicate that an actin trimer is the minimum assembly state required for tight binding to membranes. The best explanation for our data is a model in which actin oligomers assemble by binding to clustered membrane sites with successive monomers on one side of the actin filament bound to the membrane. Individual binding affinities are expected to be low, but the overall actin-membrane avidity is high, due to multivalency. Our results imply that extracellular factors that cluster membrane proteins may create sites for the formation of actin nuclei and thus trigger actin polymerization in the cell.

Rights and Permissions

Publisher PDF posted as allowed by the publisher's terms of use policy at: http://www.rupress.org/terms After the Initial Publication Period, RUP will grant to the public the non-exclusive right to copy, distribute, or display the Article under a Creative Commons Attribution-Noncommercial-Share Alike 4.0 International license, as described at https://creativecommons.org/licenses/by-nc-sa/4.0/legalcode, or updates thereof.

DOI of Published Version

10.1083/jcb.107.1.201

Source

J Cell Biol. 1988 Jul;107(1):201-9. Link to article on publisher's website

Journal/Book/Conference Title

The Journal of cell biology

Related Resources

Link to article in PubMed

PubMed ID

3392099

Creative Commons License

Creative Commons Attribution-Noncommercial 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 4.0 License.

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