Global dynamic conformational changes in the suppressor domain of IP 3 receptor by stepwise binding of the two lobes of calmodulin

Sunmi Kang, Hyuknam Kwon, He Wen, Youngmin Song, Dominique Frueh, Hee Chul Ahn, Seung Hyun Yoo, Gerhard Wagner, Sunghyouk Park

Research output: Contribution to journalArticlepeer-review

Abstract

The roles of calmodulin (CaM) have been key points of controversy in the regulation of inositol-1,4,5-trisphosphate receptor (IP3R). To address the issue, we studied the interaction between CaM and the suppressor domain of IP3R, a key allosteric regulatory domain. First, by means of a pulldown and a fluorescence titration experiment, we confirmed the interaction. Through subsequent NMR binding experiments, we observed dramatic peak disappearances of the suppressor domain on interaction with apo-CaM. The data indicated that apo-CaM induces large-scale dynamic conformational changes in the suppressor domain, involving partial unfolding and subdomain rearrangement. Analysis of the NMR data of CaM surprisingly revealed that its C lobe alone can cause such changes. Further binding experiments showed that calcium allows the free N lobe to bind to the suppressor domain, which induces extra conformational changes in both of the proteins. These results were also confirmed with CaM deletion mutants with either the N or C lobe. On the basis of this novel binding mechanism, we propose a model in which the partial unfolding of the suppressor domain by apo-CaM and the stepwise binding of the N lobe of CaM to the suppressor domain are important elements of calcium/CaM inhibition of IP3R. We believe that our working model encompasses previous regulation mechanisms of IP3R by calcium/CaM and provides new insights into the CaM-target interaction.

Original languageEnglish (US)
Pages (from-to)840-850
Number of pages11
JournalFASEB Journal
Volume25
Issue number3
DOIs
StatePublished - Mar 2011
Externally publishedYes

Keywords

  • IPR
  • Protein interaction
  • Regulation

ASJC Scopus subject areas

  • Biotechnology
  • Biochemistry
  • Molecular Biology
  • Genetics

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