Actin Activates a Cryptic Dimerization Potential of the Vinculin Tail Domain*
- From the Departments of ‡Biological Chemistry and§Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
Abstract
The tail domain of vinculin (Vt) is an actin binding module containing two regions that interact with F-actin. Although intact Vtpurified from a bacterial expression system is a globular monomer, each actin binding region dimerizes when expressed individually, suggesting the presence of cryptic self-association sites whose exposure is regulated. We show that actin modulates Vt self-association by inducing or stabilizing a conformational change in Vtthat allows dimerization. Chemical cross-linking studies implicate one of the actin binding regions in mediating dimerization in the presence of actin. Actin-induced Vt dimers may play a role in the filament cross-linking activity of this protein. The Vtdimers induced by actin are biochemically distinct from the Vt dimers and higher oligomers induced by acidic phospholipids such as phosphatidylinositol 4,5-bisphosphate, suggesting structural differences in Vt bound to these two ligands that may provide a mechanistic basis for inhibition of F-actin binding by phosphatidylinositol 4,5-bisphosphate. The ability of actin to regulate the dimerization state of an actin binding protein suggests that, rather than serving a passive structural role, actin filaments may directly participate in signal transduction and other cellular events that are known to depend on cytoskeletal integrity.
Footnotes
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↵* This work was supported by National Institutes of Health Grant GM41605.The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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↵¶ To whom correspondence should be addressed. Tel.: 410-955-3666; Fax: 410-955-5759; E-mail: scraig@jhmi.edu.
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↵1 R. P. Johnson and S. W. Craig, unpublished observations.
- Abbreviations:
- PI
-
phosphatidylinositol
- DTT
-
dithiothreitol
- DSS
-
disuccinimidyl suberate
- DSP
-
dithiobis(succinimidyl propionate)
- EDC
-
1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride
- MBS
-
m-maleidobenzoyl-N-hydroxysuccinimide ester
- PIP2
-
phosphatidylinositol 4,5-bisphosphate
- PAGE
-
polyacrylamide gel electrophoresis
- CHAPS
-
3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid
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- Received October 1, 1999.
- The American Society for Biochemistry and Molecular Biology, Inc.
