In this award, funded by the Experimental Physical Chemistry program, Professor Romesberg from The Scripps Research Institute will investigate issues relating to the evolution of protein dynamics. Proteins have evolved to perform their various biological functions that enable life; however, little is understood about how the process of evolution builds proteins for specific functions. One function central to all proteins is molecular recognition - the ability of a protein to find its binding partners within the complex milieu of the cell. Perhaps the single most remarkable system where the evolution of biological molecular recognition may be studied is the immune system, where antibodies (Abs) that recognize virtually any foreign molecule (or antigen, Ag) may be evolved from precursor (or germline) Abs within days of first encounter. The fundamental hypothesis of the proposed research is that the immune system starts with flexible and conformationally heterogeneous germline Abs that can bind a wide range of Ags with an induced-fit mechanism, and then introduces mutations that evolve them into more rigid mature Abs that bind only their target Ag with a lock-and-key mechanism. Thus, Professor Romesberg proposes that during evolution, Abs are selected based in part on a dynamic property, i.e. flexibility. To test this hypothesis, a variety of modern biophysical techniques will be employed, including nonlinear ultrafast laser spectroscopy and NMR spectroscopy, to characterize Ab dynamics and Ag-binding as a function of the specific mutations introduced during evolution. While the proposed research is focused on Abs, it should have important ramifications for how molecular recognition is evolved in other systems, such as with enzymes and their substrates or inhibitors and with signaling cascades and their signaling molecules. In addition to participating in the community outreach programs already in place at TSRI, including hosting high school student interns, presenting seminars, and participating in a lecture series at the Reuben H. Fleet Science Center in San Diego, a summer program for high school educators will be developed to bring the proposed work to a larger audience. The broader impacts of the proposed research are to introduce today's younger scientists, as well as the general public in the San Diego area, to contemporary, interdisciplinary research rooted in the fundamentals of evolution.
Normal.dotm 0 0 1 347 1979 16 3 2430 12.0 0 false 18 pt 18 pt 0 0 false false false Understanding protein dynamics, and how it is evolved, is central to understanding biological function. Perhaps the most important process in biology is molecular recognition, which allows proteins to specifically bind other proteins, cofactors, or substrates. Remarkably, antibodies (Abs) that recognize virtually any foreign molecule (or antigen, Ag) may be evolved from precursor (or germline) Abs within days of encountering it. The research conducted by Prof. Floyd E. Romesberg and his laboratory under NSF Award CHE-0848902 used a combination of experimental approaches to characterize the protein dynamics, antigen-binding properties, and structure of two separate panels of antibodies raised to two different chromophoric, small molecule antigens. The research was designed to ask a very fundamental question regarding the evolution of molecular recognition – how are Abs evolved that bind virtually any foreign Ag but not any self molecules? The laboratory’s working hypothesis is that the immune system starts with flexible and conformationally heterogeneous germline Abs that can structurally adapt to bind a wide range of Ag (i.e. an induced-fit mechanism) and evolves them into more rigid mature Abs that specifically bind only their target Ag (i.e. a lock-and-key mechanism). The dynamics or molecular flexibility of the Abs was characterized mainly using three-pulse photon echo peak shift spectroscopy, and characterization of the Abs with this method provided clear evidence that the process of somatic mutation in the immune system, or more generally, protein evolution, can have a pronounced effect on protein dynamics, supporting a connection between protein rigidity, specificity, and evolution. NMR, X-ray, and computational structure studies of the same antibodies are providing insight into the specific mechanisms by which the somatic mutations rigidify the antigen-binding sites. Broader impacts of this research program included training of high school, graduate, and postdoctoral students in a multi-/cross-disciplinary environment involving immunology, genetics, molecular biology, protein chemistry, spectroscopy, and computational chemistry. The work also increased our understanding of the most basic aspects of protein function and is anticipated to contribute to more applied protein research, such as the evolution of antibodies and other proteins for drug development.
