Assembling filamentous phage occlude pIV channels

Marciano, Denise K.; Russel, Marjorie; Simon, Sanford M.

doi:10.1073/pnas.161170398

Cited by 32 publications

(26 citation statements)

References 32 publications

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“…The pIV secretin for the filamentous phage f1 forms an ion conductive pore in planar lipid bilayers, and mutant forms of the protein allow import of molecules in whole cells to which E. coli normally is resistant (28). Entry through the pIV channel was decreased by production of phage that could not be released from the cell surface (29). The Klebsiella oxytoca secretin PulD also forms ion conductive channels in planar lipid bilayers (31).…”

Section: Discussionmentioning

confidence: 99%

A Mutant Form of the Neisseria gonorrhoeae Pilus Secretin Protein PilQ Allows Increased Entry of Heme and Antimicrobial Compounds

Chen¹,

Tobiason

Thomas³

et al. 2004

J Bacteriol

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A spontaneous point mutation in pilQ (pilQ1) resulted in phenotypic suppression of a hemoglobin (Hb) receptor mutant (hpuAB mutant), allowing gonococci to grow on Hb as the sole source of iron. PilQ, formerly designated OMP-MC, is a member of the secretin family of proteins located in the outer membrane and is required for pilus biogenesis. The pilQ1 mutant also showed decreased piliation and transformation efficiency. Insertional inactivation of pilQ1 resulted in the loss of the Hb utilization phenotype and decreased entry of free heme. Despite the ability of the pilQ1 mutant to use Hb for iron acquisition and porphyrin, there was no demonstrable binding of Hb to the cell surface. The pilQ1 mutant was more sensitive to the toxic effect of free heme in growth medium and hypersensitive to the detergent Triton X-100 and multiple antibiotics. Double mutation in pilQ1 and tonB had no effect on these phenotypes, but a double pilQ1 pilT mutant showed a reduction in Hb-dependent growth and decreased sensitivity to heme and various antimicrobial agents. Insertional inactivation of wild-type pilQ also resulted in reduced entry of heme, Triton X-100, and some antibiotics. These results show that PilQ forms a channel that allows entry of heme and certain antimicrobial compounds and that a gain-of function point mutation in pilQ results in TonB-independent, PilT-dependent increase of entry.

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Section: Discussionmentioning

confidence: 99%

A Mutant Form of the Neisseria gonorrhoeae Pilus Secretin Protein PilQ Allows Increased Entry of Heme and Antimicrobial Compounds

Chen¹,

Tobiason

Thomas³

et al. 2004

J Bacteriol

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“…The channels formed by protein export secretins are gated (48,55), and low resolution three-dimensional structures of three secretins suggest an open state for these channel proteins in the OM and a closed state in the periplasm entrance (42,44,49). Gated channels are also formed by TolC, an outer membrane protein involved in type I protein secretion and multidrug efflux (56).…”

Section: Discussionmentioning

confidence: 99%

Translocation of Group 1 Capsular Polysaccharide in Escherichia coli Serotype K30

Nesper

Hill

Paiment

et al. 2003

Journal of Biological Chemistry

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The late steps in assembly of capsular polysaccharides (CPS) and their translocation to the bacterial cell surface are not well understood. The Wza protein was shown previously to be required for the formation of the prototype group 1 capsule structure on the surface of Escherichia coli serotype K30 (Drummelsmith, J., and Whitfield, C. (2000) EMBO J. 19, 57-66). Wza is a conserved outer membrane lipoprotein that forms multimers adopting a ringlike structure, and collective evidence suggests a role for these structures in the export of capsular polymer across the outer membrane. Wza was purified in the native form and with a C-terminal hexahistidine tag. Wza His 6 was acylated and functional in capsule assembly, although its efficiency was slightly reduced in comparison to the native Wza protein. Ordered two-dimensional crystals of Wza His 6 were obtained after reconstitution of purified multimers into lipids. Electron microscopy of negatively stained crystals and Fourier filtering revealed ringlike multimers with an average outer diameter of 8.84 nm and an average central cavity diameter of 2.28 nm. Single particle analysis yielded projection structures at an estimated resolution of 3 nm, favoring a structure for the Wza His 6 containing eight identical subunits. A derivative of Wza (Wza*) in which the original signal sequence was replaced with that from OmpF showed that the native acylated N terminus of Wza is critical for formation of normal multimeric structures and for their competence for CPS assembly, but not for targeting Wza to the outer membrane. In the presence of Wza*, CPS accumulated in the periplasm but was not detected on the cell surface. Chemical cross-linking of intact cells suggested formation of a transmembrane complex minimally containing Wza and the inner membrane tyrosine autokinase Wzc.In Gram-negative bacteria, macromolecules destined for the cell surface or the extracellular environment must cross both the inner (IM) 1 and the outer membrane (OM). In protein export, where the processes are arguably best understood, secretion systems with varying complexity accomplish the translocation steps; all involve multi-enzyme complexes where an outer membrane protein (channel) is linked directly, or via helper proteins, to IM components.Cell-associated capsular polysaccharides (CPS) and their secreted (cell-free) counterparts, exopolysaccharides (EPS), represent another type of macromolecule that must be transported across the cell envelope. The early steps in assembly of these polymers are reasonably well established. However, there is little understanding of the terminal steps, including the mechanism by which they cross the bacterial cell envelope and the machinery involved.In Escherichia coli, more than 80 antigenically distinct capsular (K) polysaccharide structures are recognized. They are divided into four groups based on the organization of their genetic loci, polymerization mechanisms, and regulation (1). Group 1 and 2 capsules have received the most attention, and they involve biosynthet...

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“…Finally, this mutant pIV allows the entry of maltodextrins into the periplasm in the absence of the specific channel LamB. Marciano et al (399) showed that this entry of maltodextrin is blocked by the assembly and extrusion of f1 phage, confirming that the channel indeed serves as the exit for the phage particles.…”

Section: Secretins Ushers and Autotransporters Producing Oligomericmentioning

confidence: 98%

Molecular Basis of Bacterial Outer Membrane Permeability Revisited

Nikaido

2003

Microbiol Mol Biol Rev

3,800

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Gram-negative bacteria characteristically are surrounded by an additional membrane layer, the outer membrane. Although outer membrane components often play important roles in the interaction of symbiotic or pathogenic bacteria with their host organisms, the major role of this membrane must usually be to serve as a permeability barrier to prevent the entry of noxious compounds and at the same time to allow the influx of nutrient molecules. This review summarizes the development in the field since our previous review (H. Nikaido and M. Vaara, Microbiol. Rev. 49:1-32, 1985) was published. With the discovery of protein channels, structural knowledge enables us to understand in molecular detail how porins, specific channels, TonB-linked receptors, and other proteins function. We are now beginning to see how the export of large proteins occurs across the outer membrane. With our knowledge of the lipopolysaccharide-phospholipid asymmetric bilayer of the outer membrane, we are finally beginning to understand how this bilayer can retard the entry of lipophilic compounds, owing to our increasing knowledge about the chemistry of lipopolysaccharide from diverse organisms and the way in which lipopolysaccharide structure is modified by environmental conditions

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Assembling filamentous phage occlude pIV channels

Cited by 32 publications

References 32 publications

A Mutant Form of the Neisseria gonorrhoeae Pilus Secretin Protein PilQ Allows Increased Entry of Heme and Antimicrobial Compounds

A Mutant Form of the Neisseria gonorrhoeae Pilus Secretin Protein PilQ Allows Increased Entry of Heme and Antimicrobial Compounds

Translocation of Group 1 Capsular Polysaccharide in Escherichia coli Serotype K30

Molecular Basis of Bacterial Outer Membrane Permeability Revisited

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