Temperature dependence of myosin-II tail fragment assembly

Peggy M. McMahon, Daniel R. Hostetter, Sarah E. Rice

Research output: Contribution to journalArticle

1 Scopus citations

Abstract

Dictyostelium myosin-II bipolar thick filament (BTF) assembly is heavily dependent on ionic strength and temperature and is reversible by the phosphorylation of just three threonines. Truncated tail fragments of Dictyostelium myosin-II are commonly used as models for BTF assembly, as they self-assemble into regular paracrystals that recapitulate the ionic strength and phosphorylation dependence of full-length Dictyostelium myosin-II BTF assembly. Here we show that Dictyostelium myosin-II tail fragment assembly is highly temperature dependent, similar to full-length Dictyostelium myosin-II. Assembly of paracrystals was far more robust at 4°C than at higher temperatures. Pre-assembled paracrystals disassembled completely when shifted to 37°C, indicating that assembly does not greatly improve the thermostability of these tail fragments. The melting temperatures of individual Dictyostelium myosin-II tail coiled-coils under both low and high ionic strength conditions that prohibit paracrystal assembly are extremely low, 21°C and 28°C, respectively. These data are consistent with reversible thermal denaturation of the coiled-coil as the most likely explanation for assembly incompetence under either very low ionic strength or high temperature conditions. Assembled paracrystals of a structurally similar fragment of nonmuscle myosin-IIA were far more thermodynamically stable than their Dictyostelium counterparts at the temperatures examined here.

Original languageEnglish (US)
Pages (from-to)109-118
Number of pages10
JournalJournal of Muscle Research and Cell Motility
Volume29
Issue number2-5
DOIs
StatePublished - May 1 2008

Keywords

  • Assembly
  • Circular dichroism
  • Dictyostelium
  • Myosin-II
  • Paracrystal
  • Tail
  • Temperature

ASJC Scopus subject areas

  • Biochemistry
  • Physiology
  • Cell Biology

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