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Structural and molecular determinants for the interaction of ExbB from Serratia marcescens and HasB, a TonB paralog.

Published version
Peer-reviewed

Type

Article

Change log

Authors

Adaixo, Ricardo Jorge Diogo 
Chami, Mohamed 
Coureux, Pierre-Damien  ORCID logo  https://orcid.org/0000-0002-1328-7229
Laurent, Benoist 

Abstract

ExbB and ExbD are cytoplasmic membrane proteins that associate with TonB to convey the energy of the proton-motive force to outer membrane receptors in Gram-negative bacteria for iron uptake. The opportunistic pathogen Serratia marcescens (Sm) possesses both TonB and a heme-specific TonB paralog, HasB. ExbBSm has a long periplasmic extension absent in other bacteria such as E. coli (Ec). Long ExbB's are found in several genera of Alphaproteobacteria, most often in correlation with a hasB gene. We investigated specificity determinants of ExbBSm and HasB. We determined the cryo-EM structures of ExbBSm and of the ExbB-ExbDSm complex from S. marcescens. ExbBSm alone is a stable pentamer, and its complex includes two ExbD monomers. We showed that ExbBSm extension interacts with HasB and is involved in heme acquisition and we identified key residues in the membrane domain of ExbBSm and ExbBEc, essential for function and likely involved in the interaction with TonB/HasB. Our results shed light on the class of inner membrane energy machinery formed by ExbB, ExbD and HasB.

Description

Keywords

Escherichia coli, Serratia marcescens, Heme, Escherichia coli Proteins, Protein Binding

Journal Title

Commun Biol

Conference Name

Journal ISSN

2399-3642
2399-3642

Volume Title

5

Publisher

Springer Science and Business Media LLC