Journal of Proteomics & Bioinformatics
Open Access
ISSN: 0974-276X
+44 1223 790975
ISSN: 0974-276X
+44 1223 790975
Su Youn Lee, Moshe Giladi, Ka Young Chung and Daniel Khananshvili
Sungkyunkwan University, South Korea
Tel-Aviv University, Israel
Posters & Accepted Abstracts: J Proteomics Bioinform
Mammalian Na+/Ca2+ exchangers, NCX1 and NCX3, generate splice variants, whereas NCX2 does not. The CBD1 and CBD2 domains form a regulatory tandem (CBD12), where Ca2+ binding to CBD1 activates and Ca2+ binding to CBD2 (bearing the splicing segment) alleviates the Na+-induced inactivation. Here, the NCX2-CBD12, NCX3-CBD12-B, and NCX3-CBD12-AC proteins were analyzed by small-angle X-ray scattering (SAXS) and hydrogen-deuterium exchange massspectrometry (HDX-MS) to resolve regulatory variances in the NCX2 and NCX3 variants. SAXS revealed the unified model, according to which the Ca2+ binding to CBD12 shifts a dynamic equilibrium without generating new conformational states, and where more rigid conformational states become more populated without any global conformational changes. HDX-MS revealed the differential effects of the B and AC exons on the folding stability of apo CBD1 in NCX3-CBD12, where the dynamic differences become less noticeable in the Ca2+-bound state. Therefore, the apo forms predefine incremental changes in backbone dynamics upon Ca2+ binding. These observations may account for slower inactivation (caused by slower dissociation of occluded Ca2+ from CBD12) in the skeletal vs the brain-expressed NCX2 and NCX3 variants. This may have physiological relevance, since NCX must extrude much higher amounts of Ca2+ from the skeletal cell than from the neuron.
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 HDXMS, 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.