Ff coliphages: structural and functional relationships.

SummaryFilamentous phage use the two N-terminal domains of their gene-3-proteins to initiate infection of Escherichia coli. One domain interacts with a pilus, and then the other domain binds to TolA at the cell surface. In phage fd, these two domains are tightly associated with each other, which renders the phage robust but non-infectious, because the TolA binding site is inaccessible. Activation for infection requires partial unfolding, domain disassembly and prolyl isomerization. Phage IKe infects E. coli less efficiently than phage fd. Unlike in phage fd, the pilus-and TolAbinding domains of phage IKe are independent of each other in stability and folding. The site for TolA binding is thus always accessible, but the affinity is very low. The structures of the two domains, analysed by X-ray crystallography and by NMR spectroscopy, revealed a unique fold for the N-pilus-binding domain and a conserved fold for the TolA-binding domain. The absence of an activation mechanism as in phage fd and the low affinity for TolA probably explain the low infectivity of phage IKe. They also explain why, in a previous co-evolution experiment with a mixture of phage fd and phage IKe, all hybrid phage adopted the superior infection mechanism of phage fd.

Section: Introductionmentioning

confidence: 99%

Structural and energetic basis of infection by the filamentous bacteriophage IKe

Jakob¹,

Geitner²,

Weininger³

et al. 2012

“…1979: Chai eta/ .. 1982: Hantke, 1976: Kadner eta/., 1979Reeves. 1976: Rasched andOberer. 1986): subsequent steps of the transportation process across the envelope involve the tonB.…”

Section: Introductionmentioning

confidence: 99%

The excC gene of Escherichia coli K‐12 required for cell envelope integrity encodes the peptidoglycan‐associated lipoprotein (PAL)

Lazzaroni

Portalier

1992

117

128

The excC mutants of Escherichia coli are hypersensitive to drugs such as cholic acid and release periplasmic proteins into the extracellular medium. A 1884 bp fragment carrying the excC gene was isolated and sequenced. It contains the 3' end of the tolB gene which maps at min 17 on the E. coli map and an open reading frame which encodes the 18,748 Da ExcC protein. The protein is composed of a hydrophobic region of 22 residues and displayed an overall hydrophilic configuration. It was shown that the ExcC protein is indeed the PAL (peptidoglycan-associated lipoprotein) described by Mizuno (1979). The pal gene had not yet been characterized on the E. coli linkage map since no obvious phenotype could be identified for mutations in this gene. A topologic analysis of the PAL protein using PAL-PhoA translational fusions showed that PAL is associated with the outer membrane only by its N-terminal moiety. The carboxy-terminal part of the protein is necessary for correct interaction of PAL with the peptidoglycan layer.

“…A large number o( different filamentous phages have been isolated which share a common morphology and a circular, single-stranded DNA genome (for a review of filamentous phage structure see Makowski, 1984;Day et ai, 1988). The best studied (fi, fd, and M13) infect Eseheriehia coliwia F pili, which serve as their cell-surface receptor (for general reviews see Rasched and Oberer, 1986;Model and Russel, 1988; for a review of structure and assembly see Webster and Lopez, 1985). These three phages are very closely related, differing from one another by only a few nudeotides.…”

Section: Introductionmentioning

confidence: 99%

Filnmentous phage assembly

Russel

1991

196

127

SummaryFilamentous phages present a genetically welldefined system for studying the ordered membrane assembly of five different phage-encoded proteins around the circular single-stranded DNA phage genome. Assembly occurs at high efficiency /n vivo, catalysed by two phage-encoded membrane proteins and al least one host protein, thioredoxin. This review presents a description of the virion and its cytopiasmic precursor and summarizes the results of genetic and biochemical experiments that are beginning to elucidate the rote of the three morphogenetic proteins. The recent discovery of bacterial transport proteins with homology to a phage morphogenetic protein located in the outer membrane suggests the existence of a common mechanism for moving complex macromolecules across bacterial membranes.