A Novel Actin-bundling Kinesin-related Protein from Dictyostelium discoideum*
- § To whom correspondence should be addressed. Tel./Fax: 81-3-5454-6751; E-mail: sutoh{at}bio.c.u-tokyo.ac.jp.
Abstract
Actin filaments and microtubules are two major cytoskeletal systems involved in wide cellular processes, and the organizations of their filamentous networks are regulated by a large number of associated proteins. Recently, evidence has accumulated for the functional cooperation between the two filament systems via associated proteins. However, little is known about the interactions of the kinesin superfamily proteins, a class of microtubule-based motor proteins, with actin filaments. Here, we describe the identification and characterization of a novel kinesin-related protein named DdKin5 from Dictyostelium. DdKin5 consists of an N-terminal conserved motor domain, a central stalk region, and a C-terminal tail domain. The motor domain showed binding to microtubules in an ATP-dependent manner that is characteristic of kinesin-related proteins. We found that the C-terminal tail domain directly interacts with actin filaments and bundles them in vitro. Immunofluorescence studies showed that DdKin5 is specifically enriched at the actin-rich surface protrusions in cells. Overexpression of the DdKin5 protein affected the organization of actin filaments in cells. We propose that a kinesin-related protein, DdKin5, is a novel actin-bundling protein and a potential cross-linker of actin filaments and microtubules associated with specific actin-based structures in Dictyostelium.
Footnotes
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↵1 The abbreviations used are: KRP, kinesin-related protein; DTT, dithiothreitol; PBS, phosphate-buffered saline; GFP, green fluorescent protein; HRP, horseradish peroxidase; PIPES, 1,4-piperazinediethane-sulfonic acid; AMPPNP, adenosine 5′-(β,γ-imido)triphosphate; PBST, phosphate-buffered saline containing 0.05% Tween 20; BSA, bovine serum albumin; TRITC, tetramethylrhodamine isothiocyanate; GST, glutathione S-transferase.
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↵3 S. Iwai and K. Sutoh, unpublished observation.
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↵* This work was supported by grants-in-aid for Scientific Research from the Ministry of Education, Science, Sports, and Culture of Japan (to K. S.). The costs of publication of this article were defrayed in part by the payment of page charges. This 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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↵‡ Present address: Dept. of Applied Physics, College of Humanities and Science, Nihon University, Setagaya-ku, Tokyo 156-8550, Japan.
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- Received July 23, 2003.
- Revision received November 6, 2003.
- The American Society for Biochemistry and Molecular Biology, Inc.
