Calmodulin binding to recombinant myosin-1c and myosin-1c IQ peptides

Peter G. Gillespie, Janet L. Cyr

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

Abstract

Background: Bullfrog myosin-1c contains three previously recognized calmodulin-binding IQ domains (IQ1, IQ2, and IQ3) in its neck region; we identified a fourth IQ domain (IQ4), located immediately adjacent to IQ3. How calmodulin binds to these IQ domains is the subject of this report. Results: In the presence of EGTA, calmodulin bound to synthetic peptides corresponding to IQ1, (IQ2, and IQ3 with K)d (values of 2-4)(μ)(M at normal ionic strength; the interaction with an IQ4 peptide)was much weaker. Ca2+ substantially weakened the calmodulin-peptide affinity for all of the IQ peptides except IQ3. To reveal how calmodulin bound to the linearly arranged IQ domains of the myosin-1c neck, we used hydrodynamic measurements to determine the stoichiometry of complexes of calmodulin and myosin-1c. Purified myosin-1c and T701-Myo1c (a myosin-1c fragment with all four IQ domains and the C-terminal tail) each bound 2-3 calmodulin molecules. At a physiologically relevant temperature (25°C) and under low-Ca2+ conditions, T701-Myo1c bound two calmodulins in the absence and three calmodulins in the presence of 5 μM free calmodulin. Ca2+ dissociated nearly all calmodulins from T701-Myo1c at 25°C; one calmodulin was retained if 5 μM free calmodulin was present. Conclusions: We inferred from these data that at 25°C and normal cellular concentrations of calmodulin, calmodulin is bound to IQ1, IQ2, and IQ3 of myosin-1c when Ca2+ is low. The calmodulin bound to one of these IQ domains, probably IQ2, is only weakly associated. Upon Ca2+ elevation, all calmodulin except that bound to IQ3 should dissociate.

Original languageEnglish (US)
Article number1
Pages (from-to)1-17
Number of pages17
JournalBMC Biochemistry
Volume3
DOIs
StatePublished - Nov 26 2002

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology

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