Calcium-induced structural changes and domain autonomy in calmodulin

Finn, Bryan E.; Evenäs, Johan; Drakenberg, Torbjörn; Waltho, Jonathan P.; Thulin, Eva; Forsén, Sture

doi:10.1038/nsb0995-777

Cited by 302 publications

(292 citation statements)

References 37 publications

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“…Complementary insights were also obtained from a corresponding analysis of TnC, made by comparing the apo N-terminal domain from the X-ray crystal structure (Satyshur et al, 1994) and the N-terminal domain from the Ca2+-loaded NMR structure (Slupsky & Sykes, 1995). In all cases, the comparisons of the closed and open conformations confirm that Ca2+ binding causes opening within each of the EF-hands, as first predicted by the HMJ model based on the crystal structure of TnC (Herzberg et al, 1986), and subsequently confirmed by NMR solution structures of CaM and TnC (Finn et al, 1995;GagnC et al, 1995;Kuboniwa et al, 1995;Zhang et al, 1995).…”

Section: Caz'-induced Transition From the Closed To Open Conformationmentioning

confidence: 64%

“…a representative non-sensor protein, has been reported previously (Akke et al, 1995;Skelton et al, 1995). The general features of Ca'+-induced conformational changes in CaM and TnC were described when the structures of their apo state were first reported (Finn et al, 1995;Gagnt et al, 1995;Kuboniwa et al, 1995;Zhang et al, 1995). However, these descriptions did not reveal the underlying structural basis for the response to Ca2+ binding.…”

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confidence: 99%

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An interaction‐based analysis of calcium‐induced conformational changes in Ca²⁺ sensor proteins

1998

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Calcium sensor proteins translate transient increases in intracellular calcium levels into metabolic or mechanical responses, by undergoing dramatic conformational changes upon Ca2+ binding. A detailed analysis of the calcium binding-induced conformational changes in the representative calcium sensors calmodulin (CaM) and troponin C was performed to obtain insights into the underlying molecular basis for their response to the binding of calcium. Distance difference matrices, analysis of interresidue contacts, comparisons of interhelical angles, and inspection of structures using molecular graphics were used to make unbiased comparisons of the various structures. The calcium-induced conformational changes in these proteins are dominated by reorganization of the packing of the four helices within each domain. Comparison of the closed and open conformations confirms that calcium binding causes opening within each of the EF-hands. A secondary analysis of the conformation of the C-terminal domain of CaM (Ca"C) clearly shows that Ca"C occupies a closed conformation in the absence of calcium that is distinct from the semi-open conformation observed in the C-terminal EF-hand domains of myosin light chains. These studies provide insight into the structural basis for these changes and into the differential response to calcium binding of various members of the EF-hand calcium-binding protein family. Factors contributing to the stability of the Ca2+-loaded open conformation are discussed, including a new hypothesis that critical hydrophobic interactions stabilize the open conformation in Ca2+ sensors, but are absent in "non-sensor" proteins that remain closed upon Ca2+ binding. A role for methionine residues in stabilizing the open conformation is also proposed.

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Section: Caz'-induced Transition From the Closed To Open Conformationmentioning

confidence: 64%

mentioning

confidence: 99%

An interaction‐based analysis of calcium‐induced conformational changes in Ca²⁺ sensor proteins

1998

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“…This approach is justified by observations that the Ca2+ binding profile of free CaM can be reconstructed from those of its two isolated domains, by evidence for domain-independence in the binding and dissociation of Ca2+ in CaM-target complexes, and by the observation that individual Ca2+ site mutations perturb mainly the two sites in the same domain (Linse et al, 1991;Starovasnik et al, 1992;Finn et al, 1995;Bayley et al, 1996;Johnson et al, 1996). Table 2 presents the resulting equilibrium dissociation constants and Hill coefficients of the high-affinity ( K D l , H I ) and low affinity (KD2, Hz) CaM domains.…”

Section: Measurements Of Ca2+ Binding To Cam-peptide Complexesmentioning

confidence: 99%

“…CaM has a dumbbell shaped structure in which two domains, termed the N and C domains, are linked by a flexible helix (Taylor et al, 1991;Finn et al, 1995;Kuboniwa et al, 1995;Zhang et al, 1995). Each domain binds two Ca2+ ions into a pair of EF-hand type sites.…”

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confidence: 99%

Intermolecular tuning of calmodulin by target peptides and proteins: Differential effects on Ca²⁺ binding and implications for kinase activation

1997

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Ca2+-activated calmodulin (CaM) regulates many target enzymes by docking to an amphiphilic target helix of variable sequence. This study compares the equilibrium Ca2+ binding and Ca2+ dissociation kinetics of CaM complexed to target peptides derived from five different CaM-regulated proteins: phosphorylase kinase, CaM-dependent protein kinase 11, skeletal and smooth myosin light chain kinases, and the plasma membrane Ca2+-ATPase. The results reveal that different target peptides can tune the Ca2+ binding affinities and kinetics of the two CaM domains over a wide range of Ca2+ concentrations and time scales. The five peptides increase the Ca2+ affinity of the N-terminal regulatory domain from 14-to 350-fold and slow its Ca2+ dissociation kinetics from 60-to 140-fold. Smaller effects are observed for the C-terminal domain, where peptides increase the apparent Ca2+ affinity 8-to 100-fold and slow dissociation kinetics 13-to 32-fold. In full-length skeletal myosin light chain kinase the inter-molecular tuning provided by the isolated target peptide is further modulated by other tuning interactions, resulting in a CaM-protein complex that has a 10-fold lower Ca2+ affinity than the analogous CaM-peptide complex. Unlike the CaM-peptide complexes, Ca2+ dissociation from the protein complex follows monoexponential kinetics in which all four Ca2+ ions dissociate at a rate comparable to the slow rate observed in the peptide complex. The two Ca2+ ions bound to the CaM N-terminal domain are substantially occluded in the CaM-protein complex. Overall, the results indicate that the cellular activation of myosin light chain kinase is likely to be triggered by the binding of free CaZ2+-CaM or Cq2+-CaM after a Ca2+ signal has begun and that inactivation of the complex is initiated by a single rate-limiting event, which is proposed to be either the direct dissociation of Ca2+ ions from the bound C-terminal domain or the dissociation of Ca2+ loaded C-terminal domain from skMLCK. The observed target-induced variations in Ca2+ affinities and dissociation rates could serve to tune CaM activation and inactivation for different cellular pathways, and also must counterbalance the variable energetic costs of driving the activating conformational change in different target enzymes.Keywords: calcium signaling; calmodulin; kinase regulation; protein-protein interactionsThe ubiquitous protein calmodulin (CaM) plays a crucial role in Ca2+ signaling (Beckingham, 1995;Braun & Schulman, 1995; Clapham, 1995;Wolenski, 1995; Berridge, 1996), where it regulates a wide range of cellular processes by serving as an intracellular receptor for Ca2+ ions (Wheeler et al

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“…Comparison of the N-terminal region of Helix B of N-CaM (A) and Ca 2+ -loaded CaM (1CLL). The segments of the helix that are in a traditional alpha-helical configuration are colored rose red, while the most N-terminal portion of the helix in our structure displays a 3 10 -helical conformation and is colored magenta. The oxygen and nitrogen of residues are colored red and blue, respectively.…”

Section: Supplementary Materialsmentioning

confidence: 99%

A 1.3-Å Structure of Zinc-bound N-terminal Domain of Calmodulin Elucidates Potential Early Ion-binding Step

Warren

Guo

Tang

2007

Journal of Molecular Biology

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SummaryCalmodulin (CaM) is a 16.8 kDa calcium binding protein involved in calcium-signal transduction. It is the canonical member of the EF-hand family of proteins, which are characterized by a helixloop-helix calcium-binding motif. CaM is comprised of N-and C-terminal globular domains (NCaM and C-CaM), and within each domain there are two EF-hand motifs. Upon binding calcium, CaM undergoes a significant, global conformational change involving reorientation of the four helix bundles in each of its two domains. This conformational change upon ion binding is a key component of the signal transduction and regulatory roles of CaM, yet the precise nature of this transition is still unclear. Here, we present a 1.3Å structure of zinc-bound N-terminal calmodulin (N-CaM) solved by single wavelength anomalous diffraction (SAD) phasing of a selenomethionyl-N-CaM. Our zincbound N-CaM structure differs from previously reported CaM structures and resembles calcium-free apo-CaM despite the zinc binding to both EF-hand motifs. Structural comparison with calcium-free apo-CaM, calcium-loaded CaM, and a crosslinked calcium-loaded CaM suggests that our zinc-bound N-CaM reveals an intermediate step in the initiation of metal ion binding at the first EF-hand motif. Our data also suggests that metal ion coordination by two key residues in the first metal-binding site represents an initial step in the conformational transition induced by metal binding. This is followed by reordering of the N-terminal region of the helix exiting from this first binding loop. This conformational switch should be incorporated into models of either step-wise conformational transition or flexible, dynamic energetic state-sampling based transition.

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Calcium-induced structural changes and domain autonomy in calmodulin

Cited by 302 publications

References 37 publications

An interaction‐based analysis of calcium‐induced conformational changes in Ca²⁺ sensor proteins

An interaction‐based analysis of calcium‐induced conformational changes in Ca²⁺ sensor proteins

Intermolecular tuning of calmodulin by target peptides and proteins: Differential effects on Ca²⁺ binding and implications for kinase activation

A 1.3-Å Structure of Zinc-bound N-terminal Domain of Calmodulin Elucidates Potential Early Ion-binding Step

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Calcium-induced structural changes and domain autonomy in calmodulin

Cited by 302 publications

References 37 publications

An interaction‐based analysis of calcium‐induced conformational changes in Ca2+ sensor proteins

An interaction‐based analysis of calcium‐induced conformational changes in Ca2+ sensor proteins

Intermolecular tuning of calmodulin by target peptides and proteins: Differential effects on Ca2+ binding and implications for kinase activation

A 1.3-Å Structure of Zinc-bound N-terminal Domain of Calmodulin Elucidates Potential Early Ion-binding Step

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An interaction‐based analysis of calcium‐induced conformational changes in Ca²⁺ sensor proteins

An interaction‐based analysis of calcium‐induced conformational changes in Ca²⁺ sensor proteins

Intermolecular tuning of calmodulin by target peptides and proteins: Differential effects on Ca²⁺ binding and implications for kinase activation