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Structure and Function of the Escherichia coli Tol-Pal Stator Protein TolR

DOI: 10.1074/jbc.M115.671586 DOI Help
PMID: 26354441 PMID Help

Authors: Justyna Wojdyla (University of Oxford) , Erin Cutts (Department of Biochemistry, University of Oxford) , Renata Kaminska (University of Oxford) , Grigorios Papadakos (University of Oxford) , Jonathan T. S. Hopper (University of Oxford) , Phillip J. Stansfeld (University of Oxford) , David Staunton (University of Oxford) , Carol V. Robinson (University of Oxford) , Colin Kleanthous (University of Oxford)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Journal Of Biological Chemistry

State: Published (Approved)
Published: September 2015
Diamond Proposal Number(s): 9306

Open Access Open Access

Abstract: TolR is a 15-kDa inner membrane protein subunit of the Tol-Pal complex in Gram- negative bacteria the function of which is poorly understood. Tol-Pal is recruited to cell division sites where it is involved in maintaining the integrity of the outer membrane. TolR is related to MotB, the peptidoglycan (PG)-binding stator protein from the flagellum, suggesting it might serve a similar role in Tol-Pal. The only structure thus far reported for TolR is of the periplasmic domain from Haemophilus influenzae in which N- and C-terminal residues had been deleted (TolR62-133, E. coli numbering). H. influenzae TolR62-133 is a symmetrical dimer with a large deep cleft at the dimer interface. Here, we present the 1.7 Å crystal structure of the intact periplasmic domain of Escherichia coli TolR (TolR36-142). E. coli TolR36-142 is also dimeric but the architecture of the dimer is radically different to that of TolR62-133 due to intertwining of its N- and C-termini. TolR monomers are rotated ~180 ° relative to each other as a result of this strand-swapping, obliterating the putative PG-binding groove seen in TolR62-133. We found that removal of the strand swapped regions (TolR60-133) exposes cryptic PG binding activity that is absent in the full-length domain. We conclude that to function as a stator in the Tol-Pal complex dimeric TolR must undergo large- scale structural remodelling reminiscent of that proposed for MotB where N- and C-terminal sequences unfold in order for the protein to both reach and bind the PG layer ~90 Å away from the inner membrane.

Journal Keywords: Bacteria; Crystal Structure; Dimerization; Escherichia Coli (E. Coli); Membrane Protein; Tolr; Domain; Periplasm; Strand-Swapped

Subject Areas: Biology and Bio-materials

Instruments: I04-1-Macromolecular Crystallography (fixed wavelength)