5by4

Publication Abstract from PubMed

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 A 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 degrees 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 A away from the inner membrane.

Structure and Function of the Escherichia coli Tol-Pal Stator Protein TolR.,Wojdyla JA, Cutts E, Kaminska R, Papadakos G, Hopper JT, Stansfeld PJ, Staunton D, Robinson CV, Kleanthous C J Biol Chem. 2015 Sep 9. pii: jbc.M115.671586. PMID:26354441^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.