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Direct binding of F-actin to ponticulin, an integral plasma membrane glycoprotein
Women’s Health Research Faculty Publications
  • C. P. Chia
  • Anne L. Hitt
  • Elizabeth J. Luna, University of Massachusetts Medical School
UMMS Affiliation
Department of Cell Biology
Publication Date
Document Type
Actins; Binding, Competitive; Carrier Proteins; Cell Fractionation; Cell Membrane; Cell Movement; Chromatography, Affinity; Concanavalin A; Cytoskeleton; Dictyostelium; Electrophoresis, Gel, Two-Dimensional; Electrophoresis, Polyacrylamide Gel; Isoelectric Focusing; Membrane Glycoproteins; Microfilament Proteins; Protein Conformation; Radioligand Assay
We have developed an 125I-labeled F-actin blot overlay assay for the identification of F-actin-binding proteins after transfer to nitrocellulose from SDS-polyacrylamide gels. Two major F-actin-binding proteins from Dictyostelium discoideum, a cytoplasmic 30 kDa protein and a 17 kDa integral membrane protein, and two minor membrane polypeptides of 19 kDa and 15 kDa were detected by this method. Using F-actin affinity and immunoaffinity chromatography, the 17 kDa polypeptide was identified as ponticulin, a previously described actin-binding glycoprotein from D. discoideum plasma membranes (Wuestehube, L.J., and Luna, E.J., [1987]: J. Cell Biol. 105:1741-1751). The binding of F-actin to ponticulin on blots is specific because unlabeled F-actin competes with 125I-labeled F-actin and because G-actin does not bind. Nitrocellulose-bound ponticulin displays binding characteristics similar to those of purified plasma membranes in solution, e.g., F-actin binding is sensitive to high salt and to elevated temperatures. Under optimal conditions, 125-I-labeled F-actin blot overlays are at least as sensitive as are immunoblots with an antibody specific for ponticulin. When blotted onto nitrocellulose after 2-D gel electrophoresis, all isoforms of ponticulin and of the 19 kDa and 15 kDa polypeptides appear to bind F-actin in proportion to their abundance. Thus the actin-binding activies of these proteins do not appear to be regulated by modifications that affect isoelectric point. However, the actin-binding activity of nitrocellulose-bound ponticulin is diminished when the protein is exposed to reducing agents, suggesting an involvement of disulfide bond(s) in ponticulin function. The 125I-labeled F-actin blot overlay assay also may enable us to identify F-actin-binding proteins in other cell types and should provide a convenient method for monitoring the purification of these proteins.
DOI of Published Version
Cell Motil Cytoskeleton. 1991;18(3):164-79. Link to article on publisher's site
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Link to article in PubMed
PubMed ID
Citation Information
C. P. Chia, Anne L. Hitt and Elizabeth J. Luna. "Direct binding of F-actin to ponticulin, an integral plasma membrane glycoprotein" Vol. 18 Iss. 3 (1991) ISSN: 0886-1544 (Print)
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