Smooth muscle myosin phosphorylated at single head shows sustained mechanical activity

Hiroto Tanaka, Kazuaki Homma, Howard D. White, Toshio Yanagida, Mitsuo Ikebe*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


Smooth muscle contraction is regulated by the phosphorylation of myosin. It is well known that tonic smooth muscles can maintain force with low energy consumption (latch state); however, the molecular mechanism underlying this phenomenon is unresolved. Here we show that single-head phosphorylated smooth myosin (SHPMII) exhibits fast (∼24 s-1) and slow prolonged (∼1 s-1) actin interactions, whereas double-head phosphorylated myosin (DHPMII) predominantly exhibits the fast (∼29 s-1) interaction, suggesting that the phosphorylated head of SHPMII is mechanically as active as that of DHPMII. Both the fast and the slow actin interactions of SHPMII support the positive net mechanical displacement of actin. The actin translocating velocity of SHPMII was much slower than that of DHPMII, which is consistent with the slow actin interaction of SHPMII. We propose that the "latch state" can be explained by the motor characteristics of SHPMII that is present during the sustained phase of contraction.

Original languageEnglish (US)
Pages (from-to)15611-15618
Number of pages8
JournalJournal of Biological Chemistry
Issue number23
StatePublished - Jun 6 2008

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Cell Biology


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