Monitoring the Activity of Single Translocons

作者：Taufik Intan; Kedrov Alexej^*; Exterkate Marten; Driessen Arnold J M

来源：Journal of Molecular Biology, 2013, 425(22): 4145-4153.

DOI：10.1016/j.jmb.2013.08.012

• protein transport
• secretion
• protein oligomerization
• protein dynamics
• membrane proteins

Recent studies introduced a novel view that the SecYEG translocon functions as a monomer and interacts with the dimeric SecA ATPase, which fuels the preprotein translocation reaction. Here, we used nanodisc-reconstituted SecYEG to characterize the functional properties of single copies of the translocon. Using a method based on intermolecular Forster resonance energy transfer, we show for the first time that isolated nanodisc-reconstituted SecYEG monomers support preprotein translocation. When several copies of SecYEG were co-reconstituted within a nanodisc, no change in translocation kinetics was observed, suggesting that SecYEG oligomers do not facilitate enhanced translocation. In contrast, nanodisc-reconstituted monomers of the PrIA4 variant of SecYEG showed increased translocation rates. Experiments based on intramolecular Forster resonance energy transfer within the nanodisc-isolated monomeric SecYEG demonstrated a nucleotide-dependent opening of the channel upon interaction with SecA. In conclusion, the nanodisc-reconstituted SecYEG monomers are functional for preprotein translocation and provide a new prospect for single-molecule analysis of dynamic aspects of protein translocation.

• 出版日期2013-11-15