Honors Theses

Date of Award

2017

Document Type

Undergraduate Thesis

Department

Chemistry and Biochemistry

First Advisor

Susan Pedigo

Relational Format

Dissertation/Thesis

Abstract

Cadherins are a family of transmembrane proteins that dimerize to form junctions between cells in the presence of calcium. Due to the necessity for proper cell adhesion during cell differentiation in development, we are examining whether binding of other metallic divalent cations would disrupt calcium-sensitive dimerization of neural cadherin in vitro. Specifically, we are studying the effect of cadmium(II) on the linkage between calcium binding, dimerization, and dimer disassembly. Cadmium toxicity became recognized during the Industrial Revolution, with particular attention gained during the Itai-Itai disease outbreak in China during the 1910s. This toxicity, partnered with the role of cadherin in development and synapse physiology prompted investigation of this interaction. To simplify protein purification and subsequent experiments, a truncated version of N-cadherin containing only the first two extracellular domains and the adjoining segments was used to measure dimerization and ion binding. Using spectroscopy and circular dichroic measurements, the binding affinity of cadmium(II) for neural cadherin in the presence of variable ion concentrations was determined. Second, the ability of cadmium(II) to disrupt dimerization by calcium or to induce dimer disassembly was also tested. Data suggest that cadmium(II) binds to the calcium-binding sites and causes a conformational change. The binding of cadmium(II) to induce dimer disassembly, both on its own and in competition with divalent calcium, reveals some of the basic equilibrium properties under which this system operates. Together, these studies indicate that cadmium(II) is a potent ion, disrupting calcium-dependent dimerization at very low levels.

Included in

Chemistry Commons

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