On the quaternary structure and gating of the bacterial protein translocation channel

• Main Author: Dalal, Kush
• Language: English
• Published: University of British Columbia 2012
• Online Access: http://hdl.handle.net/2429/39949

The SecY protein-conducting channel associates with different cytosolic partners to drive the translocation of preprotein substrates across the bacterial inner membrane. In this thesis, several outstanding questions regarding the structure and function of the SecY channel are addressed. Our first study is motivated by the poorly defined interactions between the channel and its binding partners. We characterize the binding mode and stoichiometry of two SecY interacting proteins, the SecA ATPase and Syd, which each form 1:1 complexes with the channel. In the second study, we isolate the SecY dimer (i.e. two SecY channels), which is shown to be essential to activate the SecA ATPase activity and support protein transport. Analysis of SecY dimers in vivo further demonstrates that each constituent SecY copy has a different role in the translocation reaction. Finally, we discover that the SecY channel, in addition to transporting preprotein substrates, is also highly specific for monovalent anions. This selective conductance explains why translocation does cause a general membrane permeability and cell death. Our findings are discussed in the broader context of genetic, biochemical and structural information on the SecY channel and other translocation components.