Neuronal Calcium Sensor 1 (NCS1), a member of calcium binding protein superfamily, contains 190 highly conserved amino acid residues. Ca2+ binding to NCS1 protein causes a large positional shift in C-terminal EF-hands leading to an exposure of the hydrophobic crevice on protein surface that facilitates interaction with the target molecules. Previously, it has been shown that non-physiological metals such as Pb2+, bind to EF-hands in calmodulin and modulate interactions with its binding partners, leading to the Pb2+-induced neurotoxicity. Mn is a highly abundant metal in nature which has been found in human brain and associated with the several diseases like multiple sclerosis, Alzheimer’s and Parkinson’s disease and is considered as potential toxic element. Previous studies from our group showed Pb2+ and Cd2+ binding to DREAM protein that can contribute to Pb2+/Cd2+ induced neurotoxicity. Here we show that Pb2+ binds to EF-hands in apo-NCS1with a high affinity (Kd = 7.0±1.5 nM) whereas Cd2+ did not show any binding with NCS1. For the first time we investigated the Mn2+ association to NCS1 protein. This cation binds with an apparent equilibrium dissociation constant of 340±67 µM. Spectroscopic data show that Pb2+ and Mn2+binding trigger secondary and tertiary structural rearrangements of NCS1 that are analogous to those observed for Ca2+ association. In addition, Pb2+ as well as Mn2+ promote NCS1 interaction with hydrophobic molecule 1,8-ANS. Interestingly, Ca2+NCS1:1,8-ANS complex exhibits a co-operative binding of Pb2+ with Kd = 103±23 µM and n=1.57±0.06 whereas Mn2+ association to Ca2+NCS1:1,8-ANS complex is non-cooperative, with apparent Kd value of 924±185 µM. These results suggest allosteric interactions between the 1,8-ANS binding site and Pb2+ binding EF-hands. Data provided here points towards ability of EF-hands in NCS-1 to interact with various metals and a possible role of NCS1 in Pb2+/Mn2+ neurotoxicity.

Structural alteration as well as modulation of interaction between NCS1 and its downstream partners through Pb2+/Mn2+ binding

ACS Spring Meeting 2021

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.