Date of Award
Chemistry and Biochemistry
Cadherins play the vital role of mediating cell-cell adhesion in properly functioning tissues of the human body. Malfunction of these adherent cells can lead to drastic consequences like cancer metastasis. Thus, it is imperative to ensure the functionality of the molecular mechanism that drives these adhesive interactions. Of the various types, our studies specifically focused on the structure and function of the 'hinge region' in epithelial cadherin. This 'hinge region', composed of amino acid residues C9, P10, and E11, was of particular interest because it is the site of strand-swapped dimerization. The residues P10 and E11 are conserved within the classical cadherin family; the residue C9 is not. The E11 residue is the site of Ca2+ binding interaction, which confers structural tension in the protein. The neighboring positions of P10 and C9 are necessarily responsible for conveying this structural strain, which then drives the exchange of the Î²A-strands in the strand-swapped dimer. Our studies look into the essentiality of these C9 and P10 residues. Our hypothesis is that cysteine in position 9 is not required, but that proline in position 10 is. The necessity of these specific amino acids was tested by comparing wild type ECAD12 proteins to mutated ECAD12 proteins with alanine residues instead of the typical cysteine in position 9 and proline in position 10. Evidenced by the results from extensive analytical and spectroscopic tests, we concluded that the C9 residue is not essential to normal ECAD structure. Conversely, we found that the P10 residue does play a more influential role in proper ECAD conformation. This was exhibited by an increase in the stability of EC domain 2 and a change in the enthalpy of unfolding of EC domain 1 conferred by the mutated P10A protein. Surprisingly, neither mutation had an effect on the dimerization patterns of the ECAD12 protein, indicating that neither the C9 nor P10 residues are essential to strand-swapped dimerization.
Barnett, Jessica Elizabeth, "Hinge Sequence Elements in Epithelial Cadherin Form and Function" (2017). Honors Theses. 444.