Alternative pathways for association and dissociation of the calmodulin-binding domain of plasma membrane Ca2+-ATPase isoform 4b (PMCA4b)

John T. Penniston, Ariel J. Caride, Emanuel E. Strehler

Research output: Contribution to journalArticle

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Abstract

The calmodulin (CaM)-binding domain of isoform 4b of the plasma membrane Ca2+ -ATPase (PMCA) pump is represented by peptide C28. CaM binds to either PMCA or C28 by a mechanism in which the primary anchor residue Trp-1093 binds to the C-terminal lobe of the extended CaM molecule, followed by collapse of CaM with the N-terminal lobe binding to the secondary anchor Phe-1110 (Juranic, N., Atanasova, E., Filoteo, A. G., Macura, S., Prendergast, F. G., Penniston, J. T., and Strehler, E. E. (2010) J. Biol. Chem. 285, 4015-4024). This is a relatively rapid reaction, with an apparent half-time of ∼1 s. The dissociation of CaM from PMCA4b or C28 is much slower, with an overall half-time of ∼10 min. Using targeted molecular dynamics, we now show that dissociation of Ca2+-CaM from C28 may occur by a pathway in which Trp-1093, although deeply embedded in a pocket in the C-terminal lobe of CaM, leaves first. The dissociation begins by relatively rapid release of Trp-1093, followed by very slow release of Phe-1110, removal of C28, and return of CaM to its conformation in the free state. Fluorescence measurements and molecular dynamics calculations concur in showing that this alternative path of release of the PMCA4b CaM-binding domain is quite different from that of binding. The intermediate of dissociation with exposed Trp-1093 has a long lifetime (minutes) and may keep the PMCA primed for activation.

Original languageEnglish (US)
Pages (from-to)29664-29671
Number of pages8
JournalJournal of Biological Chemistry
Volume287
Issue number35
DOIs
StatePublished - Aug 24 2012

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Calcium-Transporting ATPases
Calmodulin
Cell membranes
Protein Isoforms
Cell Membrane
Association reactions
Molecular Dynamics Simulation
Anchors
Molecular dynamics
Conformations
Fluorescence
Chemical activation
Pumps
Peptides
Molecules

ASJC Scopus subject areas

  • Biochemistry
  • Cell Biology
  • Molecular Biology

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Alternative pathways for association and dissociation of the calmodulin-binding domain of plasma membrane Ca2+-ATPase isoform 4b (PMCA4b). / Penniston, John T.; Caride, Ariel J.; Strehler, Emanuel E.

In: Journal of Biological Chemistry, Vol. 287, No. 35, 24.08.2012, p. 29664-29671.

Research output: Contribution to journalArticle

Penniston, John T. ; Caride, Ariel J. ; Strehler, Emanuel E. / Alternative pathways for association and dissociation of the calmodulin-binding domain of plasma membrane Ca2+-ATPase isoform 4b (PMCA4b). In: Journal of Biological Chemistry. 2012 ; Vol. 287, No. 35. pp. 29664-29671.
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abstract = "The calmodulin (CaM)-binding domain of isoform 4b of the plasma membrane Ca2+ -ATPase (PMCA) pump is represented by peptide C28. CaM binds to either PMCA or C28 by a mechanism in which the primary anchor residue Trp-1093 binds to the C-terminal lobe of the extended CaM molecule, followed by collapse of CaM with the N-terminal lobe binding to the secondary anchor Phe-1110 (Juranic, N., Atanasova, E., Filoteo, A. G., Macura, S., Prendergast, F. G., Penniston, J. T., and Strehler, E. E. (2010) J. Biol. Chem. 285, 4015-4024). This is a relatively rapid reaction, with an apparent half-time of ∼1 s. The dissociation of CaM from PMCA4b or C28 is much slower, with an overall half-time of ∼10 min. Using targeted molecular dynamics, we now show that dissociation of Ca2+-CaM from C28 may occur by a pathway in which Trp-1093, although deeply embedded in a pocket in the C-terminal lobe of CaM, leaves first. The dissociation begins by relatively rapid release of Trp-1093, followed by very slow release of Phe-1110, removal of C28, and return of CaM to its conformation in the free state. Fluorescence measurements and molecular dynamics calculations concur in showing that this alternative path of release of the PMCA4b CaM-binding domain is quite different from that of binding. The intermediate of dissociation with exposed Trp-1093 has a long lifetime (minutes) and may keep the PMCA primed for activation.",
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AB - The calmodulin (CaM)-binding domain of isoform 4b of the plasma membrane Ca2+ -ATPase (PMCA) pump is represented by peptide C28. CaM binds to either PMCA or C28 by a mechanism in which the primary anchor residue Trp-1093 binds to the C-terminal lobe of the extended CaM molecule, followed by collapse of CaM with the N-terminal lobe binding to the secondary anchor Phe-1110 (Juranic, N., Atanasova, E., Filoteo, A. G., Macura, S., Prendergast, F. G., Penniston, J. T., and Strehler, E. E. (2010) J. Biol. Chem. 285, 4015-4024). This is a relatively rapid reaction, with an apparent half-time of ∼1 s. The dissociation of CaM from PMCA4b or C28 is much slower, with an overall half-time of ∼10 min. Using targeted molecular dynamics, we now show that dissociation of Ca2+-CaM from C28 may occur by a pathway in which Trp-1093, although deeply embedded in a pocket in the C-terminal lobe of CaM, leaves first. The dissociation begins by relatively rapid release of Trp-1093, followed by very slow release of Phe-1110, removal of C28, and return of CaM to its conformation in the free state. Fluorescence measurements and molecular dynamics calculations concur in showing that this alternative path of release of the PMCA4b CaM-binding domain is quite different from that of binding. The intermediate of dissociation with exposed Trp-1093 has a long lifetime (minutes) and may keep the PMCA primed for activation.

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