A Novel Tctex2-related Light Chain Is Required for Stability of Inner Dynein Arm I1 and Motor Function in the Chlamydomonas Flagellum

doi:10.1074/jbc.M313540200

A Novel Tctex2-related Light Chain Is Required for Stability of Inner Dynein Arm I1 and Motor Function in the Chlamydomonas Flagellum*

^‡Departments of Biochemistry and Molecular, Microbial, and Structural Biology, University of Connecticut Health Center, Farmington, Connecticut 06030-3305 and^§Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire 03755

¶ An investigator of the Patrick and Catherine Weldon Donaghue Medical Research Foundation. To whom correspondence should be addressed: Dept. of Molecular, Microbial, and Structural Biology, University of Connecticut Health Center, 263 Farmington Ave., Farmington, CT 06030-3305. Tel.: 860-679-3347; Fax: 860-679-3408; E-mail: steve{at}king2.uchc.edu.

Abstract

Tctex1 and Tctex2 were originally described in mice as putative distorters/sterility factors involved in the non-Mendelian transmission of t haplotypes. Subsequently, these proteins were found to be light chains of both cytoplasmic and axonemal dyneins. We have now identified a novel Tctex2-related protein (Tctex2b) within the Chlamydomonas flagellum. Tctex2b copurifies with inner arm I1 after both sucrose gradient centrifugation and anion exchange chromatography. Unlike the Tctex2 homologue within the outer dynein arm, analysis of a Tctex2b-null strain indicates that this protein is not essential for assembly of inner arm I1. However, a lack of Tctex2b results in an unstable dynein particle that disassembles after high salt extraction from the axoneme. Cells lacking Tctex2b swim more slowly than wild type and exhibit a reduced flagellar beat frequency. Furthermore, using a microtubule sliding assay we observed that dynein motor function is reduced in vitro. These data indicate that Tctex2b is required for the stability of inner dynein arm I1 and wild-type axonemal dynein function.

Footnotes

↵1 The abbreviations used are: HC, heavy chain; HA, hemagglutinin; IC, intermediate chain; LC, light chain; Resc., rescued; kb, kilobase; MBP, maltose-binding protein; UTR, untranslated region.
↵2 R. Patel-King and S. M. King, unpublished information.
↵3 L. M. DiBella and S. M. King, manuscript in preparation.
The nucleotide sequence(s) reported in this paper has been submitted to the GenBank™/EBI Data Bank with accession number(s) BK004867.
↵* This study was supported by Grants GM51293 (to S. M. K.) and GM51379 (to E. F. S., as a consortium agreement, P. A. Lefebvre, University of Minnesota) from the National Institutes of Health, Grant 5-FY99-766 (to E. F. S.) from the March of Dimes Birth Defects Foundation, and a postdoctoral fellowship from the Lalor Foundation (to K. W.). 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.
- Received December 10, 2003.
- Revision received January 26, 2004.
The American Society for Biochemistry and Molecular Biology, Inc.