ASB4 Dimerization (2007)

Undergraduates: Kyle Powers, Cam Patterson, Jed Ferguson, Kevin Smith and Hong Wang

Faculty Advisor: Cam Patterson
Department: Chemistry

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In stem cells that were differentiated to blood vessel cells, ASB4 (Ankyrin repeat and SOCS-box containing protein-4) was present at a much higher level when compared to the stem cells that were not becoming blood vessels. In fact, out of 20,000 genes investigated, ASB4 was the most highly differentially expressed gene in vascular cells. In the future, the ASB4 protein may be manipulated to stop blood vessel differentiation and proliferation. This could be useful in halting tumor growth and in cardiovascular disease.

A site on the ASB4 protein that is crucial to its function could be blocked to modify its function. Dimerization, which has been shown to occur between ASB4 proteins, changes the conformation and function of ASB4. Therefore, if the ASB4 site necessary for dimerization could be blocked or modified, the ASB4 protein would have a different conformation and could lose some or all of its function.

My project is to determine which part of ASB4 mediates dimerization. The ASB4 protein can be divided into ten independent functional parts: nine ankyrin repeats and a SOCS-box. I am using site-directed mutagenesis to create proteins that are missing one of these parts. Once a mutant missing once of these parts has been created, I use co-immunoprecipitation and Western blotting to determine if dimerization occurs. So far I have narrowed the dimerization culprit down to ankyrin repeats four and five. I am currently synthesizing deletion mutants for each of these ankyrin repeats. Once the ankyrin repeat that is responsible for dimerization has been discovered, I will narrow it down to the exact sequence of amino acids.