• Open Access Science Articles
  • Science Sessions: The PNAS Podcast Program

Cooperative binding of the outer arm-docking complex underlies the regular arrangement of outer arm dynein in the axoneme

  1. Ken-ichi Wakabayashig,3
  1. aDepartment of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo 113-0033, Japan;
  2. bEcoTopia Science Institute, Nagoya University, Chikusa, Nagoya 464-8602, Japan;
  3. cGraduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama 226-8510, Japan;
  4. dDepartment of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT 06030;
  5. eDepartment of Cell and Developmental Biology, University of Massachusetts Medical School, Worcester, MA 01655;
  6. fDepartment of Life Sciences, Faculty of Science, Gakushuin University, Tokyo 171-8588, Japan; and
  7. gChemical Resources Laboratory, Tokyo Institute of Technology, Yokohama 226-8503, Japan

  1. Edited by Joel L. Rosenbaum, Yale University, New Haven, CT, and accepted by the Editorial Board May 20, 2014 (received for review February 19, 2014)

Significance

In eukaryotic cilia and flagella, outer arm dyneins (OADs) are bound to axonemal doublet microtubules every 24 nm; however, how this regular arrangement is produced remains unknown. To approach this problem, we studied the properties of the OAD-docking complex (ODA-DC), a three-subunit complex that functions as the OAD-docking site on the doublet. Using recombinant ODA-DC, we found that the ODA-DC has an ∼24-nm-long ellipsoidal shape and cooperatively binds to the axoneme in an end-to-end manner. These and other results indicate that cooperative association of the ODA-DC underlies the periodic OAD arrangement at specific positions on the doublets. These findings provide insight into how the regular axonemal repeat structure is produced.

Abstract

Outer arm dynein (OAD) in cilia and flagella is bound to the outer doublet microtubules every 24 nm. Periodic binding of OADs at specific sites is important for efficient cilia/flagella beating; however, the molecular mechanism that specifies OAD arrangement remains elusive. Studies using the green alga Chlamydomonas reinhardtii have shown that the OAD-docking complex (ODA-DC), a heterotrimeric complex present at the OAD base, functions as the OAD docking site on the doublet. We find that the ODA–DC has an ellipsoidal shape ∼24 nm in length. In mutant axonemes that lack OAD but retain the ODA-DC, ODA-DC molecules are aligned in an end-to-end manner along the outer doublets. When flagella of a mutant lacking ODA-DCs are supplied with ODA-DCs upon gamete fusion, ODA-DC molecules first bind to the mutant axonemes in the proximal region, and the occupied region gradually extends toward the tip, followed by binding of OADs. This and other results indicate that a cooperative association of the ODA-DC underlies its function as the OAD-docking site and is the determinant of the 24-nm periodicity.

Footnotes

  • ↵1Present address: Advanced ICT Research Institute, National Institute of Information and Communications Technology, Kobe 651-2492, Japan.

  • ↵2Present address: Life Science Research Center, College of Bioresource Sciences, Nihon University, Fujisawa 252-0880, Japan.

  • ↵3To whom correspondence should be addressed. E-mail: wakaba{at}res.titech.ac.jp.

  • Author contributions: M.O., R.K., and K.W. designed research; M.O., A.F., J.U., F.A., and K.W. performed research; S.M.K. and G.B.W. contributed new reagents/analytic tools; M.O., A.F., J.U., F.A., and K.W. analyzed data; and M.O., S.M.K., G.B.W., R.K., and K.W. wrote the paper.

  • The authors declare no conflict of interest.

  • This article is a PNAS Direct Submission. J.L.R. is a guest editor invited by the Editorial Board.

  • This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1403101111/-/DCSupplemental.

Online Impact