Premium
Global dynamic conformational changes in the suppressor domain of IP 3 receptor by stepwise binding of the two lobes of calmodulin
Author(s) -
Kang Sunmi,
Kwon Hyuknam,
Wen He,
Song Youngmin,
Frueh Dominique,
Ahn HeeChul,
Yoo Seung Hyun,
Wagner Gerhard,
Park Sunghyouk
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fj.10-160705
Subject(s) - calmodulin , allosteric regulation , suppressor , chemistry , conformational change , biophysics , domain (mathematical analysis) , binding site , plasma protein binding , binding domain , stereochemistry , receptor , microbiology and biotechnology , biochemistry , biology , enzyme , gene , mathematical analysis , mathematics
The roles of calmodulin (CaM) have been key points of controversy in the regulation of inositol‐1,4,5‐trisphosphate receptor (IP 3 R). To address the issue, we studied the interaction between CaM and the suppressor domain of IP 3 R, 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 domainbyapo‐CaM and the stepwise binding of the N lobe of CaM to the suppressor domain are important elements of calcium/CaM inhibition of IP 3 R. We believe that our working model encompasses previous regulation mechanisms of IP 3 R by calcium/CaM and provides new insights into the CaM‐target interaction.—Kang, S., Kwon, H., Wen, H., Song, Y., Frueh, D., Ahn, H.‐C., Yoo, S. H., Wagner, G., Park, S. Global dynamic conformational changes in the suppressor domain of IP 3 receptor by stepwise binding of the two lobes of calmodulin. FASEB J. 25, 840–850 (2011). www.fasebj.org