期刊
MOLECULAR CELL
卷 52, 期 5, 页码 655-666出版社
CELL PRESS
DOI: 10.1016/j.molcel.2013.10.036
关键词
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资金
- Operational Programme for Education and Lifelong Learning [1473]
- European Social Fund and National Resources
- Onassis Foundation
- Paul Scherrer Institute [FK-05.08.1, FK-04.09.1]
- Swiss National Science Foundation [140879]
Most secretory preproteins exit bacterial cells through the protein translocase, comprising the SecYEG channel and the dimeric peripheral ATPase motor SecA. Energetic coupling to work remains elusive. We now demonstrate that translocation is driven by unusually dynamic quaternary changes in SecA. The dimer occupies several successive states with distinct protomer arrangements. SecA docks on SecYEG as a dimer and becomes functionally asymmetric. Docking occurs via only one protomer. The second protomer allosterically regulates downstream steps. Binding of one preprotein signal peptide to the SecYEG-docked SecA protomer elongates the SecA dimer and triggers the translocase holoenzyme to obtain a lower activation energy conformation. ATP hydrolysis nnonomerizes the triggered SecA dinner, causing mature chain trapping and processive translocation. This is a unique example of one protein exploiting quaternary dynamics to become a substrate receptor, a loading clamp, and a processive motor. This mechanism has widespread implications on protein translocases, chaperones, and motors.
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