An Investigation of Protein Dimerization by Exploiting the Unique Properties of Chemokines

Texas A&M Research Foundation, College Station TX

Investigators

Abstract

Chemokines (chemotactic cytokines) function in immune response and are often found to be dimers. The goal of this research is to investigate the protein-protein interactions involved in dimerization of the chemokine family of proteins. The chemokine family has two main subfamilies, the CC subfamily and the CXC subfamily. However, despite sharing the same overall fold and having moderate sequence identity, the proteins in each subfamily dimerize quite differently, using different amino acids in different regions of the protein. This structural situation is nearly unique and provides an excellent opportunity to study the details of dimer formation. Previous work supported by an NSF CAREER award has allowed the successful design and study of folded monomeric variants derived from chemokine dimers. This funding has also led to the development of several strategies designed to switch the dimer type of a chemokine variant. Experiments in the current project are designed to study the protein-protein interactions leading to dimerization. First, a screening system has been established that allows for rapid screening of randomly mutated chemokines to select for those having an alternate dimer interface. Second, the new chemokine dimers will be characterized biochemically to confirm the dimer dissociation constant and stability of the variant. Finally, nuclear magnetic resonance will be used to determine the structure of the altered dimer(s), thereby elucidating the specific amino acid contacts that allow dimerization. This work will exploit the characteristics of chemokines (having identical folds but two different dimer types) to reveal details of amino acid interactions necessary for protein dimerization that is not obtainable from simply observing known structures of dimers or from destabilizing known dimers. The work will allow a greater understanding of protein-protein interactions at a molecular level and will also provide an excellent educational experience for undergraduates, as such students, including a participant in a minority student summer program, have contributed significantly to the preliminary results that lay the groundwork for these experiments.