This study was undertaken to investigate the proposed in vivo pore function of PhoE protein, an Escherichia coli K12 outer membrane protein induced by growth under phosphate limitation and to compare it with those of the constitutive pore proteins OmpF and OmpC. Appropriate mutant strains were constructed containing only one of the proteins PhoE, OmpF or OmpC, or none of these proteins at all. ...

In this research we employed single-molecule electric recording techniques to investigate effects of the transmembrane and dipole potential on the reversible protonation of acidic residues from the constriction zone of the OmpF porin. Our results support the paradigm according to which the protonation state of aspartate 113 and glutamate 117 residues from the constriction region of OmpF is infl...

Silver-resistant mutants were selected by stepwise exposure of silver-susceptible clinical strains of Escherichia coli, two of which did not contain any plasmids, to either silver nitrate or silver sulfadiazine. These mutants showed complete cross-resistance to both compounds. They showed low-level cross-resistance to cephalosporins and HgCl2 but not to other heavy metals. The Ag-resistant muta...

We examined the ability of porins from Salmonella enterica serovar typhi to induce a long-term antibody response in BALB/c mice. These porins triggered a strong lifelong production of immunoglobulin G (IgG) antibody in the absence of exogenous adjuvant. Analysis of the IgG subclasses produced during this antibody response revealed the presence of the subclasses IgG2b, IgG1, IgG2a and weak IgG3....

To understand ion permeation, one must assign correct ionization states to titratable amino acid residues in protein channels. We report on the effects of physical and methodological assumptions in calculating the protonation states at neutral bulk pH of titratable residues lining the lumen of the native Escherichia coli OmpF channel, and five mutants. We systematically considered a wide range ...

EnvZ is a cytoplasmic membrane protein which is involved in osmoregulatory expression of the ompF and ompC genes in Escherichia coli possibly by sensing the environmental osmotic signal. A truncated form of the EnvZ protein (EnvZ*), comprising 82% of EnvZ starting from the C terminus, was purified to homogeneity. The purified EnvZ* was autophosphorylated with ATP. The phosphoryl group on EnvZ* ...

A rapid and efficient procedure for site specific mutagenesis is described. A double primed synthesis with a 17-mer mismatch primer and a "universal" 15-mer M13 sequencing primer was used to introduce a T to A transversion into an ompF signal peptide gene cloned in the M13mp8 vector. The two primers were annealed to the circular single stranded M13 template. After a short extension and ligation...

To study the role of the signal sequences in the biogenesis of outer membrane proteins, we have constructed two hybrid genes: a phoE-ompF hybrid gene, which encodes the signal sequence of outer membrane PhoE protein and the structural sequence of outer membrane OmpF protein, and a bla-phoE hybrid gene which encodes the signal sequence as well as 158 amino acids of the structural sequence of the...

Expression of the Escherichia coli outer membrane proteins, OmpC and OmpF, is regulated in response to the medium osmolarity. The OmpR and EnvZ proteins are transcriptional factors involved in this osmotic regulation of the ompC and ompF genes. In particular, expression of the ompC gene is activated by the positive regulator, OmpR, in response to high osmolarity of the medium. In this study, we...

In this paper we study the properties of pores formed by OmpF porin from Escherichia coli, based on a molecular dynamics simulation of the OmpF trimer, 318 palmitoyl-oleoyl-phosphatidylethanolamine lipids, 27 Na+ ions, and 12,992 water molecules. After equilibration and a nanosecond production run, the OmpF trimer exhibits a C-alpha root mean square deviation from the crystal structure of 0.23 ...