CAREER: Biological chemistry of Pb2+ revealed through Pb2+ mediated protein-membrane interactions

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In this CAREER award, funded by the Chemistry of Life Processes Program in the Chemistry Division, Dr. Tatyana Igumenova describes an integrated research and educational program focused on the biological chemistry of lead (Pb). Despite the well-known effect of Pb(II) exposure on humans, the molecular mechanism of Pb(II) action is poorly understood. Dr. Igumenova PI will use a synergistic structural and functional approach to conduct the first in-depth systematic investigation of Pb(II)-protein interactions. The focus is on a class of peripheral membrane proteins called conserved homology 2, or C2, domains. This protein system enables the PI to tackle an unexplored aspect of Pb(II) action: how it mediates the protein-membrane interactions. The C2 domains selected for these studies are from three parent proteins that are molecular targets of Pb(II). These proteins have different structures and functions, such as signal transduction and membrane trafficking. Dr. Igumenova has assembled a toolkit of biophysical techniques that will enable characterization of Pb(II)-protein interactions in the absence and presence of lipid membranes. The results of the proposed studies will report on how the change in the chemical environment of C2 domains, brought about by Pb(II) binding, affects the downstream reaction, which is the association of C2 with lipid membranes. These results have a potential to transform the conventional view of Pb(II) as a ligand whose action is limited to the formation of high-affinity protein complexes to a ligand that serves as a functional Ca2+ surrogate. The obtained data will enable the PI to identify the predictors of coordination geometries and Pb(II) affinities in membrane-bound and membrane-free C2 domains. This, in turn, will facilitate the identification of other potential Pb(II) targets.Lead (Pb) is a heavy metal that became enriched 1000-fold above its natural level due to human activity. The most prevalent form of lead in the environment, Pb(II), interacts with biological molecules in the cell. Many of these biological molecules are proteins that bind calcium ion under normal conditions. Lead(II) ion successfully competes with calcium ion and binds to these proteins - referred to as molecular targets of Pb(II) - with high affinity. Dr. Igumenova's objective is to determine the features of these proteins that make them bind Pb(II) more tightly than calcium ion and understand the effect of Pb(II) on protein function. One of the broader impacts of the proposed work is entry of students from under-represented groups into graduate programs. Dr. Igumenova will offer ten-week summer research internships, with recruitment facilitated by her activities as a faculty mentor in the NSF-sponsored Louis Stokes Alliance for Minority Participation (LSAMP) and Research Experience for Undergraduates (REU) programs. Professional development and mentoring of the student will be accomplished through research activities, the use of high-end research instrumentation (an 800 MHz NMR instrument), and REU-affiliated programs. As an outreach activity, Dr. Igumenova's laboratory will develop an educational web application (app): "Lead (Pb): the toxic chemistry in action" for the iPhone/iPad/iPod mobile platforms. The objective is to enhance public knowledge of the harmful effects of Pb2+ on the society, from the ancient and modern sources of Pb(II) in the environment to specific Pb(II)-complexed molecular structures generated as a result of Dr. Igumenova's research activities. The benefit for society will be an increase in public awareness to the fact that there is no safe level of Pb exposure.