The four-transmembrane protein IP39 of Euglena forms strands by a trimeric unit repeat

Hiroshi Suzuki, Yasuyuki Ito, Yuji Yamazaki, Katsuhiko Mineta, Masami Uji, Kazuhiro Abe, Kazutoshi Tani, Yoshinori Fujiyoshi*, Sachiko Tsukita

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


Euglenoid flagellates have striped surface structures comprising pellicles, which allow the cell shape to vary from rigid to flexible during the characteristic movement of the flagellates. In Euglena gracilis, the pellicular strip membranes are covered with paracrystalline arrays of a major integral membrane protein, IP39, a putative four-membrane-spanning protein with the conserved sequence motif of the PMP-22/EMP/MP20/Claudin superfamily. Here we report the three-dimensional structure of Euglena IP39 determined by electron crystallography. Two-dimensional crystals of IP39 appear to form a striated pattern of antiparallel double-rows in which trimeric IP39 units are longitudinally polymerised, resulting in continuously extending zigzag-shaped lines. Structural analysis revealed an asymmetric molecular arrangement in the trimer, and suggested that at least four different interactions between neighbouring protomers are involved. A combination of such multiple interactions would be important for linear strand formation of membrane proteins in a lipid bilayer.

Original languageEnglish (US)
Article number1766
JournalNature Communications
StatePublished - 2013
Externally publishedYes

ASJC Scopus subject areas

  • General Chemistry
  • General Biochemistry, Genetics and Molecular Biology
  • General Physics and Astronomy


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