Ligand-induced Conformational Changes via Flexible Linkers in the Amino-terminal region of the Inositol 1,4,5-Trisphosphate Receptor

Jenny Chan, Andrew E. Whitten, Cy M. Jeffries, Ivan Bosanac, Tapas K. Mal, Jennifer Ito, Horea Porumb, Takayuki Michikawa, Katsuhiko Mikoshiba, Jill Trewhella, Mitsuhiko Ikura

Research output: Contribution to journalArticle

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Abstract

Cytoplasmic Ca2+ signals are highly regulated by various ion transporters, including the inositol 1,4,5-trisphosphate (IP3) receptor (IP3R), which functions as a Ca2+ release channel on the endoplasmic reticulum membrane. Crystal structures of the two N-terminal regulatory regions from type 1 IP3R have been reported; those of the IP3-binding core (IP3RCORE) with bound IP3, and the suppressor domain. This study examines the structural effects of ligand binding on an IP3R construct, designated IP3RN, that contains both the IP3-binding core and the suppressor domain. Our circular dichroism results reveal that the IP3-bound and IP3-free states have similar secondary structure content, consistent with preservation of the overall fold within the individual domains. Thermal denaturation data show that, while IP3 has a large effect on the stability of IP3RCORE, it has little effect on IP3RN, indicating that the suppressor domain is critical to the stability of IP3RN. The NMR data for IP3RN provide evidence for chemical exchange, which may be due to protein conformational dynamics in both apo and IP3-bound states: a conclusion supported by the small-angle X-ray scattering data. Further, the scattering data show that IP3RN undergoes a change in average conformation in response to IP3 binding and the presence of Ca2+ in the solution. Taken together, these data lead us to propose that there are two flexible linkers in the N-terminal region of IP3R that join stably folded domains and give rise to an equilibrium mixture of conformational sub-states containing compact and more extended structures. IP3 binding drives the conformational equilibrium toward more compact structures, while the presence of Ca2+ drives it to a more extended set.

Original languageEnglish (US)
Pages (from-to)1269-1280
Number of pages12
JournalJournal of Molecular Biology
Volume373
Issue number5
DOIs
StatePublished - Nov 9 2007

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Inositol 1,4,5-Trisphosphate Receptors
Ligands
Inositol 1,4,5-Trisphosphate
Nucleic Acid Regulatory Sequences
Circular Dichroism
Endoplasmic Reticulum
Hot Temperature
X-Rays
Ions
Membranes
Proteins

All Science Journal Classification (ASJC) codes

  • Structural Biology
  • Molecular Biology

Cite this

Chan, Jenny ; Whitten, Andrew E. ; Jeffries, Cy M. ; Bosanac, Ivan ; Mal, Tapas K. ; Ito, Jennifer ; Porumb, Horea ; Michikawa, Takayuki ; Mikoshiba, Katsuhiko ; Trewhella, Jill ; Ikura, Mitsuhiko. / Ligand-induced Conformational Changes via Flexible Linkers in the Amino-terminal region of the Inositol 1,4,5-Trisphosphate Receptor. In: Journal of Molecular Biology. 2007 ; Vol. 373, No. 5. pp. 1269-1280.
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title = "Ligand-induced Conformational Changes via Flexible Linkers in the Amino-terminal region of the Inositol 1,4,5-Trisphosphate Receptor",
abstract = "Cytoplasmic Ca2+ signals are highly regulated by various ion transporters, including the inositol 1,4,5-trisphosphate (IP3) receptor (IP3R), which functions as a Ca2+ release channel on the endoplasmic reticulum membrane. Crystal structures of the two N-terminal regulatory regions from type 1 IP3R have been reported; those of the IP3-binding core (IP3RCORE) with bound IP3, and the suppressor domain. This study examines the structural effects of ligand binding on an IP3R construct, designated IP3RN, that contains both the IP3-binding core and the suppressor domain. Our circular dichroism results reveal that the IP3-bound and IP3-free states have similar secondary structure content, consistent with preservation of the overall fold within the individual domains. Thermal denaturation data show that, while IP3 has a large effect on the stability of IP3RCORE, it has little effect on IP3RN, indicating that the suppressor domain is critical to the stability of IP3RN. The NMR data for IP3RN provide evidence for chemical exchange, which may be due to protein conformational dynamics in both apo and IP3-bound states: a conclusion supported by the small-angle X-ray scattering data. Further, the scattering data show that IP3RN undergoes a change in average conformation in response to IP3 binding and the presence of Ca2+ in the solution. Taken together, these data lead us to propose that there are two flexible linkers in the N-terminal region of IP3R that join stably folded domains and give rise to an equilibrium mixture of conformational sub-states containing compact and more extended structures. IP3 binding drives the conformational equilibrium toward more compact structures, while the presence of Ca2+ drives it to a more extended set.",
author = "Jenny Chan and Whitten, {Andrew E.} and Jeffries, {Cy M.} and Ivan Bosanac and Mal, {Tapas K.} and Jennifer Ito and Horea Porumb and Takayuki Michikawa and Katsuhiko Mikoshiba and Jill Trewhella and Mitsuhiko Ikura",
year = "2007",
month = "11",
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doi = "10.1016/j.jmb.2007.08.057",
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Chan, J, Whitten, AE, Jeffries, CM, Bosanac, I, Mal, TK, Ito, J, Porumb, H, Michikawa, T, Mikoshiba, K, Trewhella, J & Ikura, M 2007, 'Ligand-induced Conformational Changes via Flexible Linkers in the Amino-terminal region of the Inositol 1,4,5-Trisphosphate Receptor', Journal of Molecular Biology, vol. 373, no. 5, pp. 1269-1280. https://doi.org/10.1016/j.jmb.2007.08.057

Ligand-induced Conformational Changes via Flexible Linkers in the Amino-terminal region of the Inositol 1,4,5-Trisphosphate Receptor. / Chan, Jenny; Whitten, Andrew E.; Jeffries, Cy M.; Bosanac, Ivan; Mal, Tapas K.; Ito, Jennifer; Porumb, Horea; Michikawa, Takayuki; Mikoshiba, Katsuhiko; Trewhella, Jill; Ikura, Mitsuhiko.

In: Journal of Molecular Biology, Vol. 373, No. 5, 09.11.2007, p. 1269-1280.

Research output: Contribution to journalArticle

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T1 - Ligand-induced Conformational Changes via Flexible Linkers in the Amino-terminal region of the Inositol 1,4,5-Trisphosphate Receptor

AU - Chan, Jenny

AU - Whitten, Andrew E.

AU - Jeffries, Cy M.

AU - Bosanac, Ivan

AU - Mal, Tapas K.

AU - Ito, Jennifer

AU - Porumb, Horea

AU - Michikawa, Takayuki

AU - Mikoshiba, Katsuhiko

AU - Trewhella, Jill

AU - Ikura, Mitsuhiko

PY - 2007/11/9

Y1 - 2007/11/9

N2 - Cytoplasmic Ca2+ signals are highly regulated by various ion transporters, including the inositol 1,4,5-trisphosphate (IP3) receptor (IP3R), which functions as a Ca2+ release channel on the endoplasmic reticulum membrane. Crystal structures of the two N-terminal regulatory regions from type 1 IP3R have been reported; those of the IP3-binding core (IP3RCORE) with bound IP3, and the suppressor domain. This study examines the structural effects of ligand binding on an IP3R construct, designated IP3RN, that contains both the IP3-binding core and the suppressor domain. Our circular dichroism results reveal that the IP3-bound and IP3-free states have similar secondary structure content, consistent with preservation of the overall fold within the individual domains. Thermal denaturation data show that, while IP3 has a large effect on the stability of IP3RCORE, it has little effect on IP3RN, indicating that the suppressor domain is critical to the stability of IP3RN. The NMR data for IP3RN provide evidence for chemical exchange, which may be due to protein conformational dynamics in both apo and IP3-bound states: a conclusion supported by the small-angle X-ray scattering data. Further, the scattering data show that IP3RN undergoes a change in average conformation in response to IP3 binding and the presence of Ca2+ in the solution. Taken together, these data lead us to propose that there are two flexible linkers in the N-terminal region of IP3R that join stably folded domains and give rise to an equilibrium mixture of conformational sub-states containing compact and more extended structures. IP3 binding drives the conformational equilibrium toward more compact structures, while the presence of Ca2+ drives it to a more extended set.

AB - Cytoplasmic Ca2+ signals are highly regulated by various ion transporters, including the inositol 1,4,5-trisphosphate (IP3) receptor (IP3R), which functions as a Ca2+ release channel on the endoplasmic reticulum membrane. Crystal structures of the two N-terminal regulatory regions from type 1 IP3R have been reported; those of the IP3-binding core (IP3RCORE) with bound IP3, and the suppressor domain. This study examines the structural effects of ligand binding on an IP3R construct, designated IP3RN, that contains both the IP3-binding core and the suppressor domain. Our circular dichroism results reveal that the IP3-bound and IP3-free states have similar secondary structure content, consistent with preservation of the overall fold within the individual domains. Thermal denaturation data show that, while IP3 has a large effect on the stability of IP3RCORE, it has little effect on IP3RN, indicating that the suppressor domain is critical to the stability of IP3RN. The NMR data for IP3RN provide evidence for chemical exchange, which may be due to protein conformational dynamics in both apo and IP3-bound states: a conclusion supported by the small-angle X-ray scattering data. Further, the scattering data show that IP3RN undergoes a change in average conformation in response to IP3 binding and the presence of Ca2+ in the solution. Taken together, these data lead us to propose that there are two flexible linkers in the N-terminal region of IP3R that join stably folded domains and give rise to an equilibrium mixture of conformational sub-states containing compact and more extended structures. IP3 binding drives the conformational equilibrium toward more compact structures, while the presence of Ca2+ drives it to a more extended set.

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