Molecular and structural basis of inner core lipopolysaccharide alterations in Escherichia coli: incorporation of glucuronic acid and phosphoethanolamine in the heptose region.
It is well established that lipopolysaccharide (LPS) often carries nonstoichiometric substitutions in lipid A and in the inner core. In this work, the molecular basis of inner core alterations and their physiological significance are addressed. A new inner core modification of LPS is described, which arises due to the addition of glucuronic acid on the third heptose with a concomitant loss of phosphate on the second heptose. This was shown by chemical and structural analyses. Furthermore, the gene whose product is responsible for the addition of this sugar was identified in all Escherichia coli core types and in Salmonella and was designated waaH. Its deduced amino acid sequence exhibits homology to glycosyltransferase family 2. The transcription of the waaH gene is positively regulated by the PhoB/R two-component system in a growth phase-dependent manner, which is coordinated with the transcription of the ugd gene explaining the genetic basis of this modification. Glucuronic acid modification was observed in E. coli B, K12, R2, and R4 core types and in Salmonella. We also show that the phosphoethanolamine (P-EtN) addition on heptose I in E. coli K12 requires the product of the ORF yijP, a new gene designated as eptC. Incorporation of P-EtN is also positively regulated by PhoB/R, although it can occur at a basal level without a requirement for any regulatory inducible systems. This P-EtN modification is essential for resistance to a variety of factors, which destabilize the outer membrane like the addition of SDS or challenge to sublethal concentrations of Zn(2+).
Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Parkallee 22, 23845 Borstel, Germany; Department of Microbiology, Gdansk University of Technology, Narutowicza 11/12, 80-233 Gdansk, Poland.
Gracjana
G
Klein
Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Parkallee 22, 23845 Borstel, Germany.
Sven
S
Müller-Loennies
Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Parkallee 22, 23845 Borstel, Germany.
Buko
B
Lindner
Department of Microbiology, Gdansk University of Technology, Narutowicza 11/12, 80-233 Gdansk, Poland.
Natalia
N
Kobylak
Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Parkallee 22, 23845 Borstel, Germany.
Helmut
H
Brade
Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Parkallee 22, 23845 Borstel, Germany; Department of Microbiology, Gdansk University of Technology, Narutowicza 11/12, 80-233 Gdansk, Poland. Electronic address: satish.raina@pg.gda.pl.
Satish
S
Raina
D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002462:Cell Membrane / Q000378:metabolism / Q000502:physiology; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D004983:Ethanolamines / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D020723:Glucuronic Acid / Q000378:metabolism*; D016695:Glycosyltransferases / Q000235:genetics; D006539:Heptoses / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000737:chemistry / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D058977:Molecular Sequence Annotation; D008969:Molecular Sequence Data; D014158:Transcription, Genetic
D029968:Escherichia coli Proteins; D004983:Ethanolamines; D006539:Heptoses; D008070:Lipopolysaccharides; D008565:Membrane Proteins; C121439:eptC protein, E coli; C005448:phosphorylethanolamine; D020723:Glucuronic Acid; D016695:Glycosyltransferases; C409702:WaaQ protein, E coli