Thermodynamic linkage between calmodulin domains binding calcium and contiguous sites in the C-terminal tail of Ca V1.2

T. Idil Apak Evans, Johannes W Hell, Madeline A. Shea

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


Calmodulin (CaM) binding to the intracellular C-terminal tail (CTT) of the cardiac L-type Ca 2+ channel (Ca V1.2) regulates Ca 2+ entry by recognizing sites that contribute to negative feedback mechanisms for channel closing. CaM associates with Ca V1.2 under low resting [Ca 2+], but is poised to change conformation and position when intracellular [Ca 2+] rises. CaM binding Ca 2+, and the domains of CaM binding the CTT are linked thermodynamic functions. To better understand regulation, we determined the energetics of CaM domains binding to peptides representing pre-IQ sites A 1588, and C 1614 and the IQ motif studied as overlapping peptides IQ 1644 and IQ′ 1650 as well as their effect on calcium binding. (Ca 2+) 4-CaM bound to all four peptides very favorably (K d ≤ 2 nM). Linkage analysis showed that IQ 1644-1670 bound with a K d ~ 1 pM. In the pre-IQ region, (Ca 2+) 2-N-domain bound preferentially to A 1588, while (Ca 2+) 2-C-domain preferred C 1614. When bound to C 1614, calcium binding in the N-domain affected the tertiary conformation of the C-domain. Based on the thermodynamics, we propose a structural mechanism for calcium-dependent conformational change in which the linker between CTT sites A and C buckles to form an A-C hairpin that is bridged by calcium-saturated CaM.

Original languageEnglish (US)
Pages (from-to)172-187
Number of pages16
JournalBiophysical Chemistry
Issue number1
StatePublished - Nov 2011


  • Allostery
  • Calcium
  • Calmodulin
  • Cardiac
  • Crystallography
  • Disorder tendency
  • Equilibrium binding
  • Fluorescence anisotropy
  • Gibbs free energy
  • Intrinsic disorder
  • L-type calcium channel
  • Peptide
  • Phenylalanine fluorescence
  • Protein-protein interaction
  • Recognition
  • Selectivity
  • Signal transduction
  • Thermodynamics

ASJC Scopus subject areas

  • Biochemistry
  • Biophysics
  • Organic Chemistry


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