A molecular ruler determines the repeat length in eukaryotic cilia and flagella

Science. 2014 Nov 14;346(6211):857-60. doi: 10.1126/science.1260214.


Existence of cellular structures with specific size raises a fundamental question in biology: How do cells measure length? One conceptual answer to this question is by a molecular ruler, but examples of such rulers in eukaryotes are lacking. In this work, we identified a molecular ruler in eukaryotic cilia and flagella. Using cryo-electron tomography, we found that FAP59 and FAP172 form a 96-nanometer (nm)-long complex in Chlamydomonas flagella and that the absence of the complex disrupted 96-nm repeats of axonemes. Furthermore, lengthening of the FAP59/172 complex by domain duplication resulted in extension of the repeats up to 128 nm, as well as duplication of specific axonemal components. Thus, the FAP59/172 complex is the molecular ruler that determines the 96-nm repeat length and arrangements of components in cilia and flagella.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Axonemal Dyneins / chemistry*
  • Axonemal Dyneins / genetics
  • Axonemal Dyneins / ultrastructure
  • Chlamydomonas / physiology*
  • Chlamydomonas / ultrastructure
  • Cilia / physiology
  • Cilia / ultrastructure
  • Eukaryotic Cells / physiology
  • Eukaryotic Cells / ultrastructure
  • Flagella / physiology*
  • Flagella / ultrastructure
  • Protein Conformation


  • Axonemal Dyneins