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H Nikaido

Publications and source records attributed to H Nikaido.

At least 163 records · Page 9Linked to original sources
PubMed1987

Loss of OmpC porin in a strain of Salmonella typhimurium causes increased resistance to cephalosporins during therapy.

Minimal inhibitory concentrations of cephalosporins for a strain of Salmonella typhimurium from one patient increased severalfold after starting therapy with cephalexin. The first isolate with increased resistance (S20323) and an earlier, less resistant isolate (S17069) each had a TEM-1 beta-lactamase with similar Vmax and Km values. Intact cells of S20323 grown in a high osmolality medium hydrolyzed cephalosporin substrates much more slowly than did intact cells of S17069 at low substrate concentrations, a result indicating slower diffusion of cephalosporins into S20323. In low osmolality media, S17069 produced both OmpF and OmpC porins; S20323 produced only OmpF porin. In high osmolality media with osmotic activity similar to that in the patient's tissues, synthesis of the OmpF porin was repressed in both strains and left S20323 with undetectably low levels of any porin. The increased beta-lactam resistance in S20323 is apparently a consequence of the loss of the OmpC porin.

Adult↗
PubMed1987

Sensitivity of Escherichia coli to various beta-lactams is determined by the interplay of outer membrane permeability and degradation by periplasmic beta-lactamases: a quantitative predictive treatment.

In Gram-negative bacteria, beta-lactam antibiotics must overcome two barriers, the outer membrane and the periplasmic beta-lactamase, before they reach the targets of their action, penicillin-binding proteins. Although the barrier property of the outer membrane and catalytic property of the beta-lactamases have been studied and their significance in creating beta-lactam resistance emphasized, the interaction between these two barriers has not been treated quantitatively. Such treatment shows that the sensitivity, to a variety of beta-lactams, of the Escherichia coli K-12 cells containing very different levels of chromosomally coded AmpC beta-lactamase, or a plasmid-coded TEM-type beta-lactamase, can be predicted rather accurately from the penetration rate through the outer membrane and the hydrolysis rate in the periplasm. We further propose a new parameter, 'target access index', which is a quantitative expression of the result of interaction between the two barriers, and reflects the probability of success for the antibiotic to reach the targets.

Anti-Bacterial Agents↗
PubMed1986

Biosynthesis of enterobacterial common antigen requires dTDPglucose pyrophosphorylase determined by a Salmonella typhimurium rfb gene and a Salmonella montevideo rfe gene.

In group C1 salmonellae, rfe and rff genes linked to the ilv locus specify the synthesis of a glycolipid called the enterobacterial common antigen. In contrast, in group B salmonellae the synthesis requires in addition some of the genes in the rfb cluster, the main genetic determinant of the O side chains of lipopolysaccharide. In an effort to define the biochemical functions of these rfb genes, we looked in Salmonella typhimurium LT2 (group B) for rfb mutants in which the synthesis of both enterobacterial common antigen and the O side chains would be blocked in a manner suppressible by the wild-type rfe cluster of S. montevideo, of group C1. We found one mutant with these characteristics. This rfb mutation affected the activity of dTDPglucose pyrophosphorylase (glucose-1-phosphate thymidylyltransferase, EC 2.7.7.24). Whereas the rfe cluster of S. montevideo contained a gene producing this enzyme activity, there was no evidence for the presence of such a gene in the rfe cluster of group B strains. These results also showed that the synthesis of dTDP-glucose is necessary for the biosynthesis of enterobacterial common antigen; this conclusion fits with the recent demonstration of 4-acetamido-4,6-dideoxy-D-galactose as a component of enterobacterial common antigen (Lugowski et al., Carbohydr. Res. 118:173-181, 1983), because the biosynthesis of the donor of this sugar, dTDP-4-acetamido-4,6-dideoxy-D-galactose, requires dTDPglucose pyrophosphorylase.

Antigens, Bacterial↗
PubMed1985

Accessibility of lysyl residues of Escherichia coli B/r porin (OmpF) to covalent labeling reagents of different sizes. An approach for a three-dimensional structure of a channel-forming protein.

The three-dimensional structure of Escherichia coli B/r porin (OmpF) was studied by chemical modification using activated sugars of different size. Galactose and galactosides of different penetration properties through the porin channel were oxidized by galactose oxidase, and the 6-aldehydes formed were linked to amino groups in porin by reduction with NaBH3CN. Tryptic fragments of modified and unmodified porin were separated by reversed-phase high pressure liquid chromatography and identified by amino acid and amino-terminal analysis from the known primary structure of OmpF. Modification of purified native porin trimers in beta-octylglucoside revealed three classes of amino groups: (i) those not modified by any sugars; (ii) those modified only by small sugars that diffuse rapidly through the pore, such as galactose or melibiose; and (iii) those modified by either small or large sugars, the latter including pore-impermeant sugars such as stachyose. The results suggest that the three classes of amino groups correspond, respectively, to groups buried in the trimeric molecule, those in the interior of the pore and those exposed on the surface of porin. In addition modification experiments performed on whole cells suggested that all the reactive groups modified by the pore-impermeant sugars (class iii) are located on the surface of porin exposed on the outside of the outer membrane.

Bacterial Outer Membrane Proteins↗
PubMed1985

Assignment of the gene locus for the sixth component (C6) of complement in mice to chromosome 15.

A structural locus (C-6) for the sixth component of complement in mice is assigned to chromosome 15. Three-point linkage analysis indicated that the order of loci is C-6, Gpt-1, Gdc-1, and that the map distances are 25.9 +/- 4.9 between C-6 and Gpt-1, and 36.4 +/- 5.5 between C-6 and Gdc-1. Since Gdc-1 is more distal than Gpt-1, and C-6 is 26 cM away from Gpt-1, it is estimated that the C-6 is proximal to the centromere. In addition, a new C6 form found in AKR mice is described. We propose the designation C6B for it and C-6b for the allele encoding C6B.

Alanine Transaminase↗
PubMed1985

Functional reconstitution of lens gap junction proteins into proteoliposomes.

Membranes rich in junction complexes were prepared from bovine lens, and the fragments of the membranes were reconstituted into proteoliposomes with a large excess of phosphatidylcholine and dicetylphosphate. The osmotic swelling behavior of these liposomes showed that the lens junction membranes contributed protein components that produced channels with a nominal diameter of 1.4 nm. Most preparations of lens junctions produced rates of osmotic swelling much slower than those found in proteoliposomes containing equivalent amounts of Escherichia coli porin, and we discuss several possible explanations for this observation.

Animals↗
PubMed1985

Diffusion of beta-lactam antibiotics through the porin channels of Escherichia coli K-12.

Diffusion rates of various beta-lactam antibiotics through the OmpF and OmpC porin channels of Escherichia coli K-12 were measured by the use of reconstituted proteoliposomes. The results can be interpreted on the basis of the gross physicochemical properties of the antibiotics along the following lines. (i) As noted previously (Nikaido et al., J. Bacteriol., 153:232-240, 1983), there was a monotonous dependence of the penetration rate on the hydrophobicity of the molecule among the classical monoanionic beta-lactams, and a 10-fold increase in the octanol-water partition coefficient of the uncharged molecule decreased the penetration rate by a factor of 5 to 6. (ii) Compounds with exceptionally bulky side chains, such as mezlocillin, piperacillin, and cefoperazone, showed much slower penetration rates than expected from their hydrophobicity. (iii) The substituted oxime side chain on the alpha-carbon of the substituent group at position 7 of the cephem nucleus decreased the penetration rate almost by an order of magnitude; this appears to be largely due to the steric effect. (iv) The presence of a methoxy group at position 7 of the cephalosporins also reduced the penetration rate by 20%, probably also due to the steric hindrance. (v) Zwitterionic compounds penetrated very rapidly, and the correlation between the rate and hydrophobicity appeared to be much weaker than with the monoanionic compounds. Imipenem showed the highest permeability among the compounds tested, presumably due, at least in part, to its compact molecular structure. (vi) Compounds with two negative charges penetrated more slowly than did analogs with only one negatively charged group. Among them, only moxalactam, ceftriaxone, and azthreonam showed penetration rates corresponding to, or higher than, 10% of that of imipenem.

Anti-Bacterial Agents↗
PubMed1985

Role of beta-lactam hydrolysis in the mechanism of resistance of a beta-lactamase-constitutive Enterobacter cloacae strain to expanded-spectrum beta-lactams.

Enterobacter cloacae strains producing chromosomally mediated beta-lactamase constitutively show high degrees of resistance to most of the third-generation beta-lactams. It has been proposed that this resistance is due to the nonhydrolytic binding or trapping of beta-lactams by the enzyme. We found that the outer membrane of E. cloacae strain 55M indeed had permeability to cefazolin about 14-fold lower than that of Escherichia coli, and that the number of beta-lactamase molecules produced by this constitutive mutant was exceptionally large (2 X 10(5) per cell). These conditions are expected to produce a low degree of resistance, but could not explain the high resistance level of the mutant. We showed that the beta-lactamase of this strain hydrolyzed third-generation beta-lactams at measurable rates. Although the V max for these compounds was less than 0.01% of that for cefazolin, the enzyme could hydrolyze them at rates comparable to the rate for cefazolin when the substrate concentration was near 0.1 microM, a concentration thought to be physiologically relevant for the inhibition of cell growth, because of the exceptionally high affinity of the enzyme to many third-generation compounds. Calculations based on kinetic parameters of the enzyme, outer membrane permeability, and affinity toward penicillin-binding proteins succeeded in predicting the MICs for several third-generation beta-lactams. The data suggest that hydrolysis may be more important than nonhydrolytic binding for the expression of the resistant phenotype, and that studies on the susceptibility of beta-lactams to beta-lactamases should be carried out at physiologically relevant, very low concentrations of the drug, rather than the customary very high concentrations, such as 100 microM.

Anti-Bacterial Agents↗
PubMed1985

Dimeric porin from Paracoccus denitrificans.

Paracoccus denitrificans was shown to contain a 33,000-dalton porin, which produced pores of large (1.6 to 1.8 nm) diameter. Cross-linking studies showed that the porin existed as dimers in the outer membrane.

Bacterial Outer Membrane Proteins↗
PubMed1984

Genetic polymorphism of the sixth component of complement (C6) in mice.

Immunofixation after isoelectric focusing revealed two forms of mouse C6, C6A and C6M, both of which consist of two major protein bands and one or more acidic minor bands. They were distinguishable by their different isoelectric point (pI) ranges: C6M has more acidic pI ranges (pH less than 6.2) than C6A (pH less than 6.3). C6A was found in common inbred mice of Mus musculus domesticus, while C6M was found in inbred and wild mice of M. m. molossinus (Japanese wild mice, an Asian subspecies). Breeding experiments showed that these two forms of C6 were controlled by a single codominant autosomal locus. We propose the designation C-6 for this locus with two alleles, C-6a and C-6m, which encode for C6A and C6M, respectively. Linkage analysis indicated that the locus is not closely linked to the following loci: Idh-1, agouti, Amy-1, brown, Gpd-1, Mup-1, Pgm-2, Pgm-1, albino, Hbb, Es-1, Mod-1, Sep-1, Es-3, Igh-1, beige, Es-10, Sod-1, and C-3.

Animals↗
PubMed1984

Amino acid sequence homology among the major outer membrane proteins of Escherichia coli.

Analysis of amino acid sequences reported for the major outer membrane proteins of Escherichia coli, including the porins (OmpF, OmpC, and PhoE), the phage lambda receptor (LamB), and another protein (OmpA), revealed several regions of local homology that is statistically significant. The implications of this observation are discussed in relation to the evolutionary origins of these proteins, as well as to the mechanism of export of these proteins to the outer membrane.

Amino Acid Sequence↗
PubMed1984

Porins of Brucella species.

The outer membrane of Brucella species contains two major proteins, denoted as group 2 and group 3 proteins (Verstreate et al., Infect. Immun. 35:979-989, 1982). We reconstituted proteoliposomes from the purified proteins and egg phosphatidylcholine and showed that group 2 proteins, but not a group 3 protein, had the porin activity. The influx rates of sugars of various sizes into the proteoliposomes indicated that the porin channels had apparent diameters in a range comparable to that of Escherichia coli OmpF porin and that the channels were predominantly open. Among different Brucella species, there were small but detectable differences in the channel diameter, and it was possible to explain the differential sensitivity of several Brucella species to diagnostic dyes on the basis of these observed differences.

Bacterial Proteins↗
PubMed1984

Porin from Rhodopseudomonas sphaeroides.

A protein homooligomer was purified from both the cell envelope fractions and the saline extracts of Rhodopseudomonas sphaeroides cells. This oligomer exhibited strong porin activity when reconstituted into proteoliposomes with egg phosphatidylcholine. In the saline extracts of both chemotrophically and phototrophically grown cells, the porin oligomer was the most predominant polypeptide, which produced pores whose behavior toward various sugars could be approximated by hollow cylinders of 0.62 nm in radius. The oligomer was dissociated, in the presence of EDTA, into monomers that migrated on sodium dodecyl sulfate-polyacrylamide gel electrophoresis as though their molecular weight was about 47,000. The monomer was active in the reconstitution assay and produced pores with sizes comparable to those produced by the oligomer. Circular dichroism spectra indicated the predominance of beta-sheet structure in both the oligomeric and EDTA-dissociated monomeric forms. Drastic conditions, for example, precipitation with 10% trichloroacetic acid or heating for a few hours at 100 degrees C in sodium dodecyl sulfate, were necessary to denature the protein into a form with a reduced content of beta-sheet structure.

Bacterial Proteins↗
PubMed1984

Alloantibody to a sex-influenced esterase in rats (Rattus norvegicus).

An antiserum to a serum protein from female ACI rats was produced in DONRYU rats by alloimmunization. The serum protein reacting with this antiserum was shown to be a sex-influenced esterase which is identified by zymogram techniques. Evidence for this is as follows: this protein migrated in the albumin region on agarose gel immunoelectrophoresis and was not present in sera from mature males; all rats possessing the protein were sex-influenced esterase in sera specifically disappeared after treatment with this antiserum. The attempt in ACI rats to produce antiserum to the esterases from DONRYU rats was unsuccessful.

Animals↗