Myosin VI steps via a hand-over-hand mechanism with its lever arm undergoing fluctuations when attached to actin

Ahmet Yildiz, Hyokeun Park, Dan Safer, Zhaohui Yang, Li Qiong Chen, Paul R. Selvin, H. Lee Sweeney

Research output: Contribution to journalArticle

Abstract

Myosin VI is a reverse direction myosin motor that, as a dimer, moves processively on actin with an average center-of-mass movement of ∼30 nm for each step. We labeled myosin VI with a single fluorophore on either its motor domain or on the distal of two calmodulins (CaMs) located on its putative lever arm. Using a technique called FIONA (fluorescence imaging with one nanometer accuracy), step size was observed with a standard deviation of <1.5 nm, with 0.5-s temporal resolution, and observation times of minutes. Irrespective of probe position, the average step size of a labeled head was ∼60 nm, strongly supporting a hand-over-hand model of motility and ruling out models in which the unique myosin VI insert comes apart. However, the CaM probe displayed large spatial fluctuations (presence of ATP but not ADP or no nucleotide) around the mean position, whereas the motor domain probe did not. This supports a model of myosin VI motility in which the lever arm is either mechanically uncoupled from the motor domain or is undergoing reversible isomerization for part of its motile cycle on actin.

Original languageEnglish (US)
Pages (from-to)37223-37226
Number of pages4
JournalJournal of Biological Chemistry
Volume279
Issue number36
DOIs
StatePublished - Sep 3 2004

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology

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