Structure of Trypanosoma brucei flagellum accounts for its bihelical motion

Proc Natl Acad Sci U S A. 2011 Jul 5;108(27):11105-8. doi: 10.1073/pnas.1103634108. Epub 2011 Jun 20.


Trypanosoma brucei is a parasitic protozoan that causes African sleeping sickness. It contains a flagellum required for locomotion and viability. In addition to a microtubular axoneme, the flagellum contains a crystalline paraflagellar rod (PFR) and connecting proteins. We show here, by cryoelectron tomography, the structure of the flagellum in three bending states. The PFR lattice in straight flagella repeats every 56 nm along the length of the axoneme, matching the spacing of the connecting proteins. During flagellar bending, the PFR crystallographic unit cell lengths remain constant while the interaxial angles vary, similar to a jackscrew. The axoneme drives the expansion and compression of the PFR lattice. We propose that the PFR modifies the in-plane axoneme motion to produce the characteristic trypanosome bihelical motility as captured by high-speed light microscope videography.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biophysical Phenomena
  • Cryoelectron Microscopy
  • Flagella / chemistry*
  • Flagella / physiology*
  • Flagella / ultrastructure
  • Humans
  • Models, Biological
  • Models, Molecular
  • Movement / physiology
  • Protein Conformation
  • Protozoan Proteins / chemistry
  • Protozoan Proteins / physiology
  • Protozoan Proteins / ultrastructure
  • Trypanosoma brucei brucei / chemistry*
  • Trypanosoma brucei brucei / physiology*
  • Trypanosoma brucei brucei / ultrastructure


  • Protozoan Proteins
  • paraflagellar rod proteins, Trypanosoma brucei