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Book of Abstracts: Albany 2007

category image Albany 2007
Conversation 15
June 19-23 2007

Structural Study of Serpin and Its Unique Mechanism of Inhibition

Serpins are a large family of serine and cysteine protease inhibitors. A profound conformational change is involved in their unique inhibition mechanism, but several aspects of inhibition by serpins are still controversial. In this study, the structure and dynamic of α1-antitrypsin (α1-AT), the most abundant serpin in human plasma, were studied using both synchrotron protein footprinting and hydrogen/deuterium (H/D) exchange mass spectrometry, which have been widely used for probing macromolecular structures based on their ability to probe solvent exposure and structural lability in proteins. Synchrotron protein footprinting examines the conformation by determining the solvent accessibility of side chain structures of protein molecules, while H/D exchange method monitors the solvent exposure, hydrogen bonding and dynamics of amide hydrogens on the protein backbone. In our study, both methods gave consistent structural information on alpha1-AT structure. In general, regions with high oxidation rates also showed high H/D exchange rates. For example, the surface loop reactive center loop (RCL) is highly solvent accessible and flexible. In contrast, some regions with slow H/D exchange rates were difficult to oxidize. For example, beta-stands 3A and 5A, which play a key role in the conformational change, are found by both methods to be highly stable in the active form of alpha1-AT. To the best of our knowledge, this is the first report to compare these two methodologies and analyze their complementarity. Besides the uncomplexed serpin, the complex structure of α1-AT with its native protease, human neutrophile elastase, was studied using synchrotron footprinting. Comparing the two forms of serpin provides us insights of its highly unusual inhibition mechanism.

Xiaojing Zheng1, *
Yuko Tsutsui2
Patrick L. Wintrode2
Mark R. Chance1, 2

1Case Center for Proteomics and Mass Spectrometry
2Department of Physiology and Biophysics
Case Western Reserve University
Cleveland, Ohio 44106

*Email: xiaojing.zheng@case.edu