The C-terminal tail of the bacterial translocation ATPase SecA modulates its activity

Research output: Contribution to journalArticle

Authors

  • Kazi Fahmida Rahman
  • Max Wynne
  • Gareth W Hughes
  • Günter Kramer
  • Bernd Bukau
  • Damon Huber

External organisations

  • Center for Molecular Biology, Heidelberg University, Heidelberg, Germany.
  • Center for Molecular Biology, University of Heidelberg, Heidelberg, Germany.

Abstract

In bacteria, the translocation of proteins across the cytoplasmic membrane by the Sec machinery requires the ATPase SecA. SecA binds ribosomes and recognises nascent substrate proteins, but the molecular mechanism of nascent substrate recognition is unknown. We investigated the role of the C-terminal tail (CTT) of SecA in nascent polypeptide recognition. The CTT consists of a flexible linker (FLD) and a small metal-binding domain (MBD). Phylogenetic analysis and ribosome binding experiments indicated that the MBD interacts with 70S ribosomes. Disruption of the MBD only or the entire CTT had opposing effects on ribosome binding, substrate-protein binding, ATPase activity and in vivo function, suggesting that the CTT influences the conformation of SecA. Site-specific crosslinking indicated that F399 in SecA contacts ribosomal protein uL29, and binding to nascent chains disrupts this interaction. Structural studies provided insight into the CTT-mediated conformational changes in SecA. Our results suggest a mechanism for nascent substrate protein recognition.

Details

Original languageEnglish
Article numbere48385
Number of pages23
JournalElife
Volume8
Publication statusPublished - 27 Jun 2019

Keywords

  • E. coli, SAXS, SecA, biochemistry, chemical biology, metal-binding domain, molecular biophysics, protein secretion, protein translocation, ribosome, structural biology