USING WAXS TO STUDY MOLTEN GLOBULE STATES OF PROTEINS

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Previous studies by our group at the APS have demonstrated that wide angle x-ray scattering (WAXS) from proteins in solution is highly sensitive to changes in secondary, tertiary and quaternary protein structure. It is particularly powerful when applied to dynamic or flexible systems such as partially folded proteins or ensembles of structure states which are not usually amenable to x-ray crystallography. Although there is a considerable body of literature on the transition of proteins from the native to the molten globule to the unfolded states, there still exists a considerable lack of understanding of what and how much structure is present in the intermediate molten globule state. This proposal seeks to use WAXS analysis of native, molten globule and denatured states of well-characterized proteins to elucidate the nature of the molten globule state. WAXS data will be collected from proteins such as apomyoglobin; lactalbumin, ubiquitin and lactoglobulin which have been induced to undergo molten globule formation and denaturation. Using methods of analysis developed in our studies of protein breathing, we will characterize the dynamics of the molten globule state of each of these proteins. These results will be compared to theoretical structure ensemble predictions performed by T. Sosnick at the University of Chicago. These studies will be followed by time-resolved WAXS studies of the more stable (in terms of life-time) intermediates within the protein group studied in order to follow both the changes in structure and dynamics during the formation of folding intermediates in these systems.