Substitutions in the BamA β-barrel domain overcome the conditional lethal phenotype of a ΔbamB ΔbamE strain of Escherichia coli

Rene Jr Tellez, Rajeev Misra

Research output: Contribution to journalArticle

32 Citations (Scopus)

Abstract

BamA interacts with the BamBCDE lipoproteins, and together they constitute the essentialβ-barrel assembly machine (BAM) of Escherichia coli. The simultaneous absence of BamB and BamE confers a conditional lethal phenotype and a severe β-barrel outer membrane protein (OMP) biogenesis defect. Without BamB and BamE, wild-type BamA levels are significantly reduced, and the folding of the BamAβ-barrel, as assessed by the heat-modifiability assay, is drastically compromised. Single-amino-acid substitutions in the β-barrel domain of BamA improve both bacterial growth and OMP biogenesis in a bamB bamE mutant and restore BamA levels close to the BamB + BamE + level. The substitutions alter BamAβ-barrel folding, and folding in the mutants becomes independent of BamB and BamE. Remarkably, BamAβ-barrel alterations also improve OMP biogenesis in cells lacking the major periplasmic chaperone, SurA, which, together with BamB, is thought to facilitate the transfer of partially folded OMPs to the soluble POTRA (polypeptide-transport-associated) domain of BamA. Unlike the bamB bamE mutant background, the absence of BamB or SurA does not affect BamAβ-barrel folding. Thus, substitutions in the outer membrane-embedded BamA β-barrel domain overcome OMP biogenesis defects that occur at the POTRA domain of BamA in the periplasm. Based on the structure of FhaC, the altered BamA residues are predicted to lie on a highly conserved loop that folds inside theβ-barrel and in regions pointing outside theβ-barrel, suggesting that they influence BamA function by both direct and indirect mechanisms.

Original languageEnglish (US)
Pages (from-to)317-324
Number of pages8
JournalJournal of Bacteriology
Volume194
Issue number2
DOIs
StatePublished - Jan 2012

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Membrane Proteins
Escherichia coli
Phenotype
Bacterial Outer Membrane Proteins
Periplasm
Peptides
Amino Acid Substitution
Lipoproteins
Hot Temperature
Membranes
Growth

ASJC Scopus subject areas

  • Microbiology
  • Molecular Biology

Cite this

Substitutions in the BamA β-barrel domain overcome the conditional lethal phenotype of a ΔbamB ΔbamE strain of Escherichia coli. / Tellez, Rene Jr; Misra, Rajeev.

In: Journal of Bacteriology, Vol. 194, No. 2, 01.2012, p. 317-324.

Research output: Contribution to journalArticle

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