Doctor Sergei Sukharev
Department of Biology
University of Maryland
College Park, Maryland

Informal

Wednesday, April 19, 2000
3:00 pm (CT)
3269 Beckman Institute

Abstract

Previously, we have isolated the MscL channel protein from the E. coli cell envelope and gathered an essential set of energetic, spatial and kinetic parameters for the opening transition. The recently determined 3-D crystal structure of the MscL homolog from Mycobacterium tuberculosis solved in its closed state now provides a strong framework for determination of precise conformations and intramolecular interactions that permit the channel to open at a certain membrane tension. In collaboration with Dr. Robert Guy (NIH) we modeled the open and intermediate conformations for MscL. Following the data of kinetic analysis, in our models we "uncoupled" the expansion of the protein from the pore opening and discovered that the channel gate can not be placed within the of the transmembrane domain, as was previously proposed. Instead, we concluded that the gating must be accomplished by the previously unresolved N-terminal domains. We designed double cysteine mutants and confirmed the predicted conformations of the gate and of the transmembrane barrel with disulfide trapping and patch-clamp experiments. The discussion will include spatial and hydration factors that may set the tension threshold for channel activation.

Tea and coffee will be served in R3151 Beckman Institute at 2:15pm.