Arsenic is an elemental metalloid found in high concentrations in some parts of the earth’s crust.1 Inorganic arsenic-induced toxicity has adverse effects on human health and it is ranked first in the agency for toxic substances and disease registry’s (ATSDR) 2019 substance priority
list. 2 Hence it is necessary to understand its distribution and develop sensing systems with high selectivity and specificity to prevent arsenic exposure. 3 Arsenic binding proteins such as ArsR
and ArsD have exhibited exceptional selectivity to inorganic arsenite and antimonite. 4,5 To understand the mechanism of arsenic binding to proteins, mass spectrometry (MS) can be used as a valuable tool. While X-Ray crystallography and Nuclear Mangnetic Resonance spectroscopy do not facilitate protein analysis in their dynamic state, MS has advanced in understanding the intact proteins and their metal bound forms. In 1988, Franz Hillenkamp and Michael Karas showed that proteins can be made to ‘fly’ and analysed in the gas phase through Matrix assisted laser desorption ionization MS (MALDI MS). 6 Following this, many other soft
ionization techniques such as electrospray ionization (ESI) have facilitated the mass spectrometric analysis of proteins to explore their structure, non-covalent and covalent metal interactions, binding stoichiometry and kinetics. Ion mobility mass spectrometry (IM MS)
helps understand the stoichiometry, conformational changes and ligand interactions of protein metal complexes.
7 Tandem mass spectrometry is an excellent tool in understanding the metalprotein binding stoichiometries and identifying amino acids at the binding sites through collision induced dissociation (CID) of protein molecules in the gas phase.8 Hydrogen/deuterium exchange (HDX) is often coupled with MS to gain insights on protein metal binding with respect to the surface area of the protein available for the hydrogen
exchange.9 These experimental studies can be complemented with the computational approaches to better explore the protein-metal interactions. The research proposal aims to employ MS to understand the arsenite binding proteins from the prospect of developing a metal
sensing platform. References:
(1) Mukherjee, S.; Gupte, T.; Jenifer, S. K.; Thomas, T.; Pradeep, T. Arsenic in Water:
Speciation, Sources, Distribution, and Toxicology. Encyclopedia of Water. December 29, 2019, pp 1–17. https://doi.org/10.1002/9781119300762.wsts0053.
(2) ATSDR’s Substance Priority List https://www.atsdr.cdc.gov/spl/index.html.
(3) Mukherjee, S.; Gupte, T.; Jenifer, S. K.; Thomas, T.; Pradeep, T. Arsenic in Water: Fundamentals of Measurement and Remediation. Encyclopedia of Water. December 29, 2019, pp 1–11. https://doi.org/10.1002/9781119300762.wsts0054.
(4) Ajees, A.; Yang, J.; Rosen., B. P. The ArsD As(III) Metallochaperone. Biometals
2011, 24 (3), 391–399. https://doi.org/10.1007/s10534-010-9398-x.
(5) Prabaharan, C.; Kandavelu, P.; Packianathan, C.; Rosen, B. P.; Thiyagarajan, S. Structures of Two ArsR As(III)-Responsive Transcriptional Repressors: Implications for the Mechanism of Derepression. J. Struct. Biol. 2019, 207 (2), 209–217.
https://doi.org/10.1016/j.jsb.2019.05.009. (6) Karas, M.; Hillenkamp, F. Laser Desorption Ionization of Proteins with Molecular Masses Exceeding 10,000 Daltons. Anal. Chem. 1988, 60 (20), 2299–2301 https://doi.org/10.1021/ac00171a028.
(7) Ghosh, D.; Baksi, A.; Mudedla, S. K.; Nag, A.; Ganayee, M. A.; Subramanian, V.; Pradeep, T. Gold-Induced Unfolding of Lysozyme: Toward the Formation of Luminescent Clusters. J. Phys. Chem. C 2017, 121 (24), 13335–13344.
https://doi.org/10.1021/acs.jpcc.7b02436.
(8) Lu, M.; Wang, H.; Wang, Z.; Li, X.-F.; Le, X. C. Identification of Reactive Cysteines in a Protein Using Arsenic Labeling and Collision-Induced Dissociation Tandem Mass Spectrometry. J. Proteome Res. 2008, 7 (8), 3080–3090.
https://doi.org/10.1021/pr700662y. (9) Ghosh, D.; Mudedla, S. K.; Islam, M. R.; Subramanian, V.; Pradeep, T. Conformational Changes of Protein upon Encapsulation of Noble Metal Clusters: An Investigation by Hydrogen/Deuterium Exchange Mass Spectrometry. J. Phys. Chem. C 2019, 123 (28), 17598–17605. https://doi.org/10.1021/acs.jpcc.9b04009.