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Function of the head-tail junction in the activity of myosin II

Takeshi Haraguchi1, Kei Honda, Yuichi Wanikawa

  • 1Department of Biology, Graduate School of Science, Chiba University, Inage-ku, Chiba 263-8522, Japan.

Biochemical and Biophysical Research Communications
|September 18, 2013
PubMed

Insights

The Pro-Leu-Leu sequence in myosin II is crucial for actin-activated ATPase activity. Mutations affecting the first leucine significantly decrease this activity, impacting myosin head cooperativity.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Muscle Physiology

Background:

  • Class II myosins possess a conserved Pro-Leu-Leu motif at their head-tail junctions.
  • This motif's role in myosin function, particularly in actin-myosin interactions, remains incompletely understood.

Purpose of the Study:

  • To investigate the functional significance of the Pro-Leu-Leu sequence in smooth muscle heavy meromyosin (HMM).
  • To elucidate the impact of specific mutations within this sequence on actin-activated ATPase activity and actin-sliding velocity.

Main Methods:

  • Site-directed mutagenesis was employed to alter the Pro-Leu-Leu sequence in smooth muscle HMM.
  • Actin-activated ATPase activity and actin-sliding velocity were measured to assess the effects of mutations.
  • ADP release rates from acto-HMM were analyzed in mutant constructs.

Main Results:

  • Deletion of proline and the second leucine had minimal impact on ATPase activity and sliding velocity.
  • Deletion of both leucines or substitution of the first leucine with alanine significantly reduced actin-activated ATPase activity (14-fold and 5-fold, respectively).
  • Actin-sliding velocity and ADP release rates were largely unaffected by these mutations, suggesting a role beyond simple binding kinetics.

Conclusions:

  • The first leucine of the conserved Leu-Leu sequence is critical for modulating the cooperativity between myosin heads.
  • This sequence element profoundly influences the actin-activated ATPase activity of myosin II, likely through inter-head communication.
Keywords:
ATPaseActinCoiled-coilHMMIn vitro motilityMyosinS1Smooth muscleWTheavy meromyosinsubfragment-1wild type

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