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Mapping the Ca2 + induced structural change in calreticulin

Boelt, Sanne Grundvad; Norn, Christoffer LU ; Rasmussen, Morten Ib; André, Ingemar LU ; Čiplys, Evaldas; Slibinskas, Rimantas; Houen, Gunnar and Højrup, Peter (2016) In Journal of Proteomics 142. p.138-148
Abstract

Calreticulin is a highly conserved multifunctional protein implicated in many different biological systems and has therefore been the subject of intensive research. It is primarily present in the endoplasmatic reticulum where its main functions are to regulate Ca2 + homeostasis, act as a chaperone and stabilize the MHC class I peptide-loading complex. Although several high-resolution structures of calreticulin exist, these only cover three-quarters of the entire protein leaving the extended structures unsolved. Additionally, the structure of calreticulin is influenced by the presence of Ca2 +. The conformational changes induced by Ca2 + have not been determined yet as they are hard to study with... (More)

Calreticulin is a highly conserved multifunctional protein implicated in many different biological systems and has therefore been the subject of intensive research. It is primarily present in the endoplasmatic reticulum where its main functions are to regulate Ca2 + homeostasis, act as a chaperone and stabilize the MHC class I peptide-loading complex. Although several high-resolution structures of calreticulin exist, these only cover three-quarters of the entire protein leaving the extended structures unsolved. Additionally, the structure of calreticulin is influenced by the presence of Ca2 +. The conformational changes induced by Ca2 + have not been determined yet as they are hard to study with traditional approaches. Here, we investigated the Ca2 +-induced conformational changes with a combination of chemical cross-linking, mass spectrometry, bioinformatics analysis and modelling in Rosetta. Using a bifunctional linker, we found a large Ca2 +-induced change to the cross-linking pattern in calreticulin. Our results are consistent with a high flexibility in the P-loop, a stabilization of the acidic C-terminal and a relatively close interaction of the P-loop and the acidic C-terminal. Biological significance The function of calreticulin, an endoplasmatic reticulin chaperone, is affected by fluctuations in Ca2 + concentration, but the structural mechanism is unknown. The present work suggests that Ca2 +-dependent regulation is caused by different conformations of a long proline-rich loop that changes the accessibility to the peptide/lectin-binding site. Our results indicate that the binding of Ca2 + to calreticulin may thus not only just be a question of Ca2 + storage but is likely to have an impact on the chaperone activity.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
BS d, Calreticulin, Chemical cross-linking, Mass spectrometry, MassAI software, Protein structure, Rosetta modelling
in
Journal of Proteomics
volume
142
pages
11 pages
publisher
Elsevier
external identifiers
  • scopus:84973889238
  • wos:000378468900015
ISSN
1874-3919
DOI
10.1016/j.jprot.2016.05.015
language
English
LU publication?
yes
id
c33c8e43-a5ea-4c46-881b-15241d4ebd61
date added to LUP
2017-02-15 09:16:37
date last changed
2017-09-18 11:32:29
@article{c33c8e43-a5ea-4c46-881b-15241d4ebd61,
  abstract     = {<p>Calreticulin is a highly conserved multifunctional protein implicated in many different biological systems and has therefore been the subject of intensive research. It is primarily present in the endoplasmatic reticulum where its main functions are to regulate Ca<sup>2 +</sup> homeostasis, act as a chaperone and stabilize the MHC class I peptide-loading complex. Although several high-resolution structures of calreticulin exist, these only cover three-quarters of the entire protein leaving the extended structures unsolved. Additionally, the structure of calreticulin is influenced by the presence of Ca<sup>2 +</sup>. The conformational changes induced by Ca<sup>2 +</sup> have not been determined yet as they are hard to study with traditional approaches. Here, we investigated the Ca<sup>2 +</sup>-induced conformational changes with a combination of chemical cross-linking, mass spectrometry, bioinformatics analysis and modelling in Rosetta. Using a bifunctional linker, we found a large Ca<sup>2 +</sup>-induced change to the cross-linking pattern in calreticulin. Our results are consistent with a high flexibility in the P-loop, a stabilization of the acidic C-terminal and a relatively close interaction of the P-loop and the acidic C-terminal. Biological significance The function of calreticulin, an endoplasmatic reticulin chaperone, is affected by fluctuations in Ca<sup>2 +</sup> concentration, but the structural mechanism is unknown. The present work suggests that Ca<sup>2 +</sup>-dependent regulation is caused by different conformations of a long proline-rich loop that changes the accessibility to the peptide/lectin-binding site. Our results indicate that the binding of Ca<sup>2 +</sup> to calreticulin may thus not only just be a question of Ca<sup>2 +</sup> storage but is likely to have an impact on the chaperone activity.</p>},
  author       = {Boelt, Sanne Grundvad and Norn, Christoffer and Rasmussen, Morten Ib and André, Ingemar and Čiplys, Evaldas and Slibinskas, Rimantas and Houen, Gunnar and Højrup, Peter},
  issn         = {1874-3919},
  keyword      = {BS d,Calreticulin,Chemical cross-linking,Mass spectrometry,MassAI software,Protein structure,Rosetta modelling},
  language     = {eng},
  month        = {01},
  pages        = {138--148},
  publisher    = {Elsevier},
  series       = {Journal of Proteomics},
  title        = {Mapping the Ca<sup>2 +</sup> induced structural change in calreticulin},
  url          = {http://dx.doi.org/10.1016/j.jprot.2016.05.015},
  volume       = {142},
  year         = {2016},
}