| Summary: | Sulfur, an essential element required by the cell for the biosynthesis of crucial compounds, such as amino acids, co-factors and vitamins, is found most abundantly in the form of sulfate. In order to cross the lipid bilayer for cell usage, sulfate, being a negatively charged ion, requires an energetically `friendly' passageway. This could be accomplished via an ion channel that allows the flow of sulfate into the cell along its concentration gradient, or via an active transport system that allows sulfate to be taken up by the cell when it is in scarcity in the environment, against its concentration gradient, like the ABC transporter and sodium or proton-coupled symporters. The subject of this dissertation, CysZ, is a bacterial sulfate transport protein that does not belong to any known superfamily of canonical transporters or channels with no distinguishing features that could hint at its functional mechanism. We have undertaken a structural and functional approach to further understanding the role of CysZ in sulfate transport. In this dissertation, we report the structure of CysZ, its functional role in sulfate uptake and have suggested a mechanistic hypothesis for the passage of sulfate through CysZ along with the exciting future directions that might follow.
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