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conferenceseries
.com
Volume 10, Issue 8 (Suppl)
J Proteomics Bioinform, an open access journal
ISSN: 0974-276X
Structural Biology 2017
September 18-20, 2017
9
th
International Conference on
Structural Biology
September 18-20, 2017 Zurich, Switzerland
Structural study of allosteric signal propagation in splice variants of Na+/Ca2+ exchanger (NCX)
Su Youn Lee
1
, Moshe Giladi
2
, Ka Young Chung
1
and
Daniel Khananshvili
2
1
Sungkyunkwan University, South Korea
2
Tel-Aviv University, Israel
T
heCa
2+
dependent allosteric regulationofNa
+
/Ca
2+
exchanger (NCX1-3) proteins are essential for handlingCa
2+
homeostasis
in many cell-types. Eukaryotic NCX variants contain regulatory calcium-binding domains (CBD1 and CBD2), which are
associated either with activation, inhibition or no response to regulatory Ca
2+
. CBD1 contains a high affinity Ca
2+
sensor
(which is highly conserved among splice variants), whereas primary information upon Ca
2+
binding to CBD1 is modified by
alternative splicing of CBD2, yielding the diverse regulatory responses to Ca
2+
. Recent studies revealed that the Ca
2+
binding
to CBD1 (Ca3–Ca4) sites results in interdomain tethering of CBDs, which rigidifies CBDs movements with accompanied slow
dissociation of occluded Ca
2+
. To resolve the structure-dynamic determinants of splicing-dependent regulation, we tested two-
domain tandem (CBD12) constructs possessing either positive (CBD12-1.4), negative (CBD12-1.1) or no response (CBD12-
1.2) to Ca
2+
using hydrogen–deuterium exchange mass spectrometry (HDX–MS). Combined with previously resolved
crystallographic structures of CBD12, the data revealed that Ca
2+
binding to CBD1 rigidifies the main-chain flexibility of
CBD2 (but not of CBD1), whereas CBD2 stabilizes the apo-CBD1. Remarkably, the extent and strength of Ca
2+
dependent
rigidification of CBD2 is splice-variant dependent, the main-chain rigidification spans from the Ca
2+
binding sites of CBD1
and propagates up to the tip of CBD2 [>50 Å (1 Å=0.1 nm)] through α helix of CBD2 (positioned at the domains’ interface) in
the splice variant exhibiting a positive response to regulatory Ca
2+
, on the other hand, the Ca
2+
-dependent rigidification stops
at the α helix of CBD2 in the splice variant with an inhibitory response. These results provide a structure-dynamic basis by
which alternative splicing diversifies the regulatory responses to Ca
2+
as well as controls the extent and strength of allosteric
signal propagation over long distance.
Biography
Su Youn Lee is currently studying the structures of drug-target proteins in her PhD program. She has been trained to study the structures of proteins using HDX-
MS, which provides information about the conformational change of proteins. She has collaborated with an expert in the NCX field and played a significant role
in a project which elaborated the dynamics and the structural mechanism of NCX regulation. And the results of this study have been published on major journals
(
Biochem J
2015
, FASEB J
2016, and
Scientific Reports
2017). Her study will contribute in suggesting a new NCX drug target sites, which will increase the
selectivity and effectiveness and reduce side effects of NCX targeting drugs.
youn3887@hanmail.netSu Youn Lee et al., J Proteomics Bioinform 2017, 10:8(Suppl)
DOI: 10.4172/0974-276X-C1-0101