Thermodynamic linkage between calmodulin domains binding calcium and contiguous sites in the C-terminal tail of Ca(V)1.2

T Idil Apak Evans; Johannes W Hell; Madeline A Shea

doi:10.1016/j.bpc.2011.06.007

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Thermodynamic linkage between calmodulin domains binding calcium and contiguous sites in the C-terminal tail of Ca(V)1.2

Journal article

Peer reviewed

Thermodynamic linkage between calmodulin domains binding calcium and contiguous sites in the C-terminal tail of Ca(V)1.2

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

Biophysical chemistry, Vol.159(1), pp.172-187

11/2011

DOI: 10.1016/j.bpc.2011.06.007

PMCID: PMC3340011

PMID: 21757287

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Abstract

Calmodulin (CaM) binding to the intracellular C-terminal tail (CTT) of the cardiac L-type Ca(2+) channel (Ca(V)1.2) regulates Ca(2+) entry by recognizing sites that contribute to negative feedback mechanisms for channel closing. CaM associates with Ca(V)1.2 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.

Thermodynamics

Amino Acid Sequence

Catalytic Domain

Calmodulin - metabolism

Calcium - metabolism

Models, Molecular

Molecular Sequence Data

Rats

Animals

Protein Binding

Calcium Channels, L-Type - metabolism

Calmodulin - chemistry

Calcium Channels, L-Type - chemistry

Details

Title: Subtitle: Thermodynamic linkage between calmodulin domains binding calcium and contiguous sites in the C-terminal tail of Ca(V)1.2
Creators: T Idil Apak Evans - Department of Biochemistry, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, IA 52242-1109, United States. idil-apak@uiowa.edu
Johannes W Hell
Madeline A Shea
Resource Type: Journal article
Publication Details: Biophysical chemistry, Vol.159(1), pp.172-187
DOI: 10.1016/j.bpc.2011.06.007
PMID: 21757287
PMCID: PMC3340011
NLM abbreviation: Biophys Chem
ISSN: 0301-4622
eISSN: 1873-4200
Publisher: Netherlands
Grant note: T32 HL 07121-30 / NHLBI NIH HHS AG0175002 / NIA NIH HHS GM57001 / NIGMS NIH HHS NIHF32 GM 77927 / NIGMS NIH HHS T32 HL007121 / NHLBI NIH HHS R01 AG017502 / NIA NIH HHS F32 GM077927 / NIGMS NIH HHS R01 GM057001-08 / NIGMS NIH HHS R01 GM057001 / NIGMS NIH HHS
Language: English
Date published: 11/2011
Academic Unit: Molecular Physiology and Biophysics; Anatomy and Cell Biology; Iowa Neuroscience Institute; Biochemistry and Molecular Biology
Record Identifier: 9984025394002771

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