Uncovering the early stages of domain melting in calmodulin with ultrafast temperature-jump infrared spectroscopy

Lucy Minnes, Gregory M. Greetham, Daniel J. Shaw, Ian P. Clark, Robby Fritzsch, Michael Towrie, Anthony W. Parker, Alistair J. Henry, Richard J. Taylor, Neil T. Hunt

Research output: Contribution to journalArticle

Abstract

The signaling protein calmodulin (CaM) undergoes a well-known change in secondary structure upon binding Ca2+, but the structural plasticity of the Ca2+-free apo state is linked to CaM functionality. Variable temperature studies of apo-CaM indicate two structural transitions at 46 and 58 °C that are assigned to melting of the C- and N-terminal domains, respectively, but the molecular mechanism of domain unfolding is unknown. We report temperature-jump time-resolved infrared (IR) spectroscopy experiments designed to target the first steps in the C-terminal domain melting transition of human apo-CaM. A comparison of the nonequilibrium relaxation of apo-CaM with the more thermodynamically stable holo-CaM, with 4 equiv of Ca2+ bound, shows that domain melting of apo-CaM begins on microsecond time scales with α-helix destabilization. These observations enable the assignment of previously reported dynamics of CaM on hundreds of microsecond time scales to thermally activated melting, producing a complete mechanism for thermal unfolding of CaM.

LanguageEnglish
Pages8733-8739
Number of pages7
JournalJournal of Physical Chemistry B
Volume123
Issue number41
Early online date26 Sep 2019
DOIs
Publication statusPublished - 17 Oct 2019

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Calmodulin
calmodulin
Infrared spectroscopy
Melting
infrared spectroscopy
melting
Temperature
temperature
destabilization
plastic properties
helices
Plasticity
proteins

Keywords

  • calmodulin
  • CaM
  • thermal melting

Cite this

Minnes, Lucy ; Greetham, Gregory M. ; Shaw, Daniel J. ; Clark, Ian P. ; Fritzsch, Robby ; Towrie, Michael ; Parker, Anthony W. ; Henry, Alistair J. ; Taylor, Richard J. ; Hunt, Neil T. / Uncovering the early stages of domain melting in calmodulin with ultrafast temperature-jump infrared spectroscopy. In: Journal of Physical Chemistry B . 2019 ; Vol. 123, No. 41. pp. 8733-8739.
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Uncovering the early stages of domain melting in calmodulin with ultrafast temperature-jump infrared spectroscopy. / Minnes, Lucy; Greetham, Gregory M.; Shaw, Daniel J.; Clark, Ian P.; Fritzsch, Robby; Towrie, Michael; Parker, Anthony W.; Henry, Alistair J.; Taylor, Richard J.; Hunt, Neil T.

In: Journal of Physical Chemistry B , Vol. 123, No. 41, 17.10.2019, p. 8733-8739.

Research output: Contribution to journalArticle

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