Myosin XI-I is mechanically and enzymatically unique among class-xi myosins in arabidopsis

Takeshi Haraguchi, Motoki Tominaga, Akihiko Nakano, Keiichi Yamamoto, Kohji Ito*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

11 Citations (Scopus)


Arabidopsis possesses 13 genes encoding class-XI myosins. Among these, myosin XI-I is phylogenetically distant. To examine the molecular properties of Arabidopsis thaliana myosin XI-I (At myosin XI-I), we performed in vitro mechanical and enzymatic analyses using recombinant constructs of At myosin XI-I. Unlike other biochemically studied class-XI myosins, At myosin XI-I showed extremely low actinactivated ATPase activity (Vmax = 3.7 Pi s1 head1). The actin-sliding velocity of At myosin XI-I was 0.25 mm s1, >10 times lower than those of other class-XI myosins. The ADP dissociation rate from acto-At myosin XI-I was 17 s1, accounting for the low actin-sliding velocity. In contrast, the apparent affinity for actin in the presence of ATP, estimated from Kapp (0.61 mM) of actin-activated ATPase, was extremely high. The equilibrium dissociation constant for actin was very low in both the presence and absence of ATP, indicating a high affinity for actin. To examine At myosin XI-I motility in vivo, green fluorescent protein-fused full-length At myosin XI-I was expressed in cultured Arabidopsis cells. At myosin XI-I localized not only on the nuclear envelope but also on small dots moving slowly (0.23 mm s1) along actin filaments. Our results show that the properties of At myosin XI-I differ from those of other Arabidopsis class-XI myosins. The data suggest that At myosin XI-I does not function as a driving force for cytoplasmic streaming but regulates the organelle velocity, supports processive organelle movement or acts as a tension generator.

Original languageEnglish
Pages (from-to)1732-1743
Number of pages12
JournalPlant and Cell Physiology
Issue number8
Publication statusPublished - 2016 Aug 1


  • ATPase
  • Actin
  • Arabidopsis
  • Kinetics
  • Molecular motor
  • Myosin

ASJC Scopus subject areas

  • Physiology
  • Plant Science
  • Cell Biology


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