Single-molecule folding mechanisms of the apo- and Mg2+-bound states of human neuronal calcium sensor-1

Mohsin M Naqvi; Pétur Orri Heiðarsson; Mariela R Otazo; Alessandro Mossa; Birthe Brandt Kragelund; Ciro Cecconi

doi:10.1016/j.bpj.2015.05.028

Single-molecule folding mechanisms of the apo- and Mg²⁺-bound states of human neuronal calcium sensor-1

Mohsin M Naqvi, Pétur Orri Heiðarsson, Mariela R Otazo, Alessandro Mossa, Birthe Brandt Kragelund, Ciro Cecconi

Biomolecular Sciences

5 Citations (Scopus)

Abstract

Abstract Neuronal calcium sensor-1 (NCS-1) is the primordial member of a family of proteins responsible primarily for sensing changes in neuronal Ca²⁺ concentration. NCS-1 is a multispecific protein interacting with a number of binding partners in both calcium-dependent and independent manners, and acting in a variety of cellular processes in which it has been linked to a number of disorders such as schizophrenia and autism. Despite extensive studies on the Ca²⁺-activated state of NCS proteins, little is known about the conformational dynamics of the Mg²⁺-bound and apo states, both of which are populated, at least transiently, at resting Ca²⁺ conditions. Here, we used optical tweezers to study the folding behavior of individual NCS-1 molecules in the presence of Mg²⁺ and in the absence of divalent ions. Under tension, the Mg²⁺-bound state of NCS-1 unfolds and refolds in a three-state process by populating one intermediate state consisting of a folded C-domain and an unfolded N-domain. The interconversion at equilibrium between the different molecular states populated by NCS-1 was monitored in real time through constant-force measurements and the energy landscapes underlying the observed transitions were reconstructed through hidden Markov model analysis. Unlike what has been observed with the Ca²⁺-bound state, the presence of Mg²⁺ allows both the N- and C-domain to fold through all-or-none transitions with similar refolding rates. In the absence of divalent ions, NCS-1 unfolds and refolds reversibly in a two-state reaction involving only the C-domain, whereas the N-domain has no detectable transitions. Overall, the results allowed us to trace the progression of NCS-1 folding along its energy landscapes and provided a solid platform for understanding the conformational dynamics of similar EF-hand proteins.

Original language	English
Journal	Biophysical Journal
Volume	109
Issue number	1
Pages (from-to)	113-123
Number of pages	11
ISSN	0006-3495
DOIs	https://doi.org/10.1016/j.bpj.2015.05.028
Publication status	Published - 9 Jul 2015

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title = "Single-molecule folding mechanisms of the apo- and Mg2+-bound states of human neuronal calcium sensor-1",

abstract = "Abstract Neuronal calcium sensor-1 (NCS-1) is the primordial member of a family of proteins responsible primarily for sensing changes in neuronal Ca2+ concentration. NCS-1 is a multispecific protein interacting with a number of binding partners in both calcium-dependent and independent manners, and acting in a variety of cellular processes in which it has been linked to a number of disorders such as schizophrenia and autism. Despite extensive studies on the Ca2+-activated state of NCS proteins, little is known about the conformational dynamics of the Mg2+-bound and apo states, both of which are populated, at least transiently, at resting Ca2+ conditions. Here, we used optical tweezers to study the folding behavior of individual NCS-1 molecules in the presence of Mg2+ and in the absence of divalent ions. Under tension, the Mg2+-bound state of NCS-1 unfolds and refolds in a three-state process by populating one intermediate state consisting of a folded C-domain and an unfolded N-domain. The interconversion at equilibrium between the different molecular states populated by NCS-1 was monitored in real time through constant-force measurements and the energy landscapes underlying the observed transitions were reconstructed through hidden Markov model analysis. Unlike what has been observed with the Ca2+-bound state, the presence of Mg2+ allows both the N- and C-domain to fold through all-or-none transitions with similar refolding rates. In the absence of divalent ions, NCS-1 unfolds and refolds reversibly in a two-state reaction involving only the C-domain, whereas the N-domain has no detectable transitions. Overall, the results allowed us to trace the progression of NCS-1 folding along its energy landscapes and provided a solid platform for understanding the conformational dynamics of similar EF-hand proteins.",

author = "Naqvi, {Mohsin M} and Hei{\dh}arsson, {P{\'e}tur Orri} and Otazo, {Mariela R} and Alessandro Mossa and Kragelund, {Birthe Brandt} and Ciro Cecconi",

year = "2015",

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doi = "10.1016/j.bpj.2015.05.028",

language = "English",

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T1 - Single-molecule folding mechanisms of the apo- and Mg2+-bound states of human neuronal calcium sensor-1

AU - Naqvi, Mohsin M

AU - Heiðarsson, Pétur Orri

AU - Otazo, Mariela R

AU - Mossa, Alessandro

AU - Kragelund, Birthe Brandt

AU - Cecconi, Ciro

PY - 2015/7/9

Y1 - 2015/7/9

N2 - Abstract Neuronal calcium sensor-1 (NCS-1) is the primordial member of a family of proteins responsible primarily for sensing changes in neuronal Ca2+ concentration. NCS-1 is a multispecific protein interacting with a number of binding partners in both calcium-dependent and independent manners, and acting in a variety of cellular processes in which it has been linked to a number of disorders such as schizophrenia and autism. Despite extensive studies on the Ca2+-activated state of NCS proteins, little is known about the conformational dynamics of the Mg2+-bound and apo states, both of which are populated, at least transiently, at resting Ca2+ conditions. Here, we used optical tweezers to study the folding behavior of individual NCS-1 molecules in the presence of Mg2+ and in the absence of divalent ions. Under tension, the Mg2+-bound state of NCS-1 unfolds and refolds in a three-state process by populating one intermediate state consisting of a folded C-domain and an unfolded N-domain. The interconversion at equilibrium between the different molecular states populated by NCS-1 was monitored in real time through constant-force measurements and the energy landscapes underlying the observed transitions were reconstructed through hidden Markov model analysis. Unlike what has been observed with the Ca2+-bound state, the presence of Mg2+ allows both the N- and C-domain to fold through all-or-none transitions with similar refolding rates. In the absence of divalent ions, NCS-1 unfolds and refolds reversibly in a two-state reaction involving only the C-domain, whereas the N-domain has no detectable transitions. Overall, the results allowed us to trace the progression of NCS-1 folding along its energy landscapes and provided a solid platform for understanding the conformational dynamics of similar EF-hand proteins.

AB - Abstract Neuronal calcium sensor-1 (NCS-1) is the primordial member of a family of proteins responsible primarily for sensing changes in neuronal Ca2+ concentration. NCS-1 is a multispecific protein interacting with a number of binding partners in both calcium-dependent and independent manners, and acting in a variety of cellular processes in which it has been linked to a number of disorders such as schizophrenia and autism. Despite extensive studies on the Ca2+-activated state of NCS proteins, little is known about the conformational dynamics of the Mg2+-bound and apo states, both of which are populated, at least transiently, at resting Ca2+ conditions. Here, we used optical tweezers to study the folding behavior of individual NCS-1 molecules in the presence of Mg2+ and in the absence of divalent ions. Under tension, the Mg2+-bound state of NCS-1 unfolds and refolds in a three-state process by populating one intermediate state consisting of a folded C-domain and an unfolded N-domain. The interconversion at equilibrium between the different molecular states populated by NCS-1 was monitored in real time through constant-force measurements and the energy landscapes underlying the observed transitions were reconstructed through hidden Markov model analysis. Unlike what has been observed with the Ca2+-bound state, the presence of Mg2+ allows both the N- and C-domain to fold through all-or-none transitions with similar refolding rates. In the absence of divalent ions, NCS-1 unfolds and refolds reversibly in a two-state reaction involving only the C-domain, whereas the N-domain has no detectable transitions. Overall, the results allowed us to trace the progression of NCS-1 folding along its energy landscapes and provided a solid platform for understanding the conformational dynamics of similar EF-hand proteins.

U2 - 10.1016/j.bpj.2015.05.028

DO - 10.1016/j.bpj.2015.05.028

M3 - Journal article

C2 - 26153708

SN - 0006-3495

VL - 109

SP - 113

EP - 123

JO - Biophysical Journal

JF - Biophysical Journal

IS - 1

ER -

Single-molecule folding mechanisms of the apo- and Mg2+-bound states of human neuronal calcium sensor-1

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Single-molecule folding mechanisms of the apo- and Mg²⁺-bound states of human neuronal calcium sensor-1