Interaction of the motor protein SecA and the bacterial protein translocation channel SecYEG in the absence of ATP

Klemens Winkler, Andreas Karner, Andreas Horner, Christof Hannesschlaeger, Denis Knyazev, Christine Siligan, Mirjam Zimmermann, Roland Kuttner, Peter Pohl, Johannes Preiner

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

Translocation of many secretory proteins through the bacterial plasma membrane is facilitated by a complex of the SecYEG channel with the motor protein SecA. The ATP-free complex is unstable in detergent, raising the question how SecA may perform several rounds of ATP hydrolysis without being released from the membrane embedded SecYEG. Here we show that dual recognition of (i) SecYEG and (ii) vicinal acidic lipids confers an apparent nanomolar affinity. High-speed atomic force microscopy visualizes the complexes between monomeric SecA and SecYEG as being stable for tens of seconds. These long-lasting events and complementary shorter ones both give rise to single ion channel openings of equal duration. Furthermore, luminescence resonance energy transfer reveals two conformations of the SecYEG-SecA complex that differ in the protrusion depth of SecA's two-helix finger into SecYEG's aqueous channel. Such movement of the finger is in line with the power stroke mechanism of protein translocation.

Original languageEnglish
Pages (from-to)3431-3443
Number of pages13
JournalNanoscale Advances
Volume2
Issue number8
DOIs
Publication statusPublished - Aug 2020

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