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Confirming the Revised C-Terminal Domain of the MscL Crystal Structure

Joshua A. Maurer ^* , Donald E. Elmore  , Daniel Clayton , Li Xiong , Henry A. Lester  and Dennis A. Dougherty 

^* Department of Chemistry, Washington University, St. Louis, Missouri 63130; Department of Chemistry, Wellesley College, Wellesley, Massachusetts 02482; and Division of Chemistry and Chemical Engineering and Division of Biology, California Institute of Technology, Pasadena, California 91125

Correspondence: Address reprint requests to Joshua A. Maurer, Dept. of Chemistry, Washington University, St. Louis, MO 63130. Tel.: 314-935-4695; E-mail: maurer{at}wustl.edu; or Donald E. Elmore, Dept. of Chemistry, Wellesley College, Wellesley, MA 02482. Tel.: 781-283-3171; E-mail: delmore{at}wellesley.edu.

The structure of the C-terminal domain of the mechanosensitive channel of large conductance (MscL) has generated significant controversy. As a result, several structures have been proposed for this region: the original crystal structure (1MSL) of the Mycobacterium tuberculosis homolog (Tb), a model of the Escherichia coli homolog, and, most recently, a revised crystal structure of Tb-MscL (2OAR). To understand which of these structures represents a physiological conformation, we measured the impact of mutations to the C-terminal domain on the thermal stability of Tb-MscL using circular dichroism and performed molecular dynamics simulations of the original and the revised crystal structures of Tb-MscL. Our results imply that this region is helical and adopts an -helical bundle conformation similar to that observed in the E. coli MscL model and the revised Tb-MscL crystal structure.