Comparison of outer membrane porin proteins produced by Escherichia coli and Salmonella typhimurium

The OmpC, OmpF, and Lc (NmpC) porin proteins of Escherichia coli K-12 have been shown to be similar to the OmpC (36K), OmpF (35K) and OmpD (34K) porin proteins of Salmnella typhimurium LT2 in terms of function, regulation of expression, and, in the case of OmpC and OmpF proteins, equivalence of the genetic loci determining their production. However, the corresponding pairs of proteins from these two species showed only limited similarity in peptide maps and no similarity in terms of migration on polyacrylamide gels.     

Analyses of genetic variants of l-glycerol-3-phosphate dehydrogenase in Drosophila melanogaster by two-dimensional gel electrophoresis and immunoelectrophoresis

A protein spot corresponding to l-glycerol-3-phosphate dehydrogenase (α-GPDH, E.C. 1.1.1.8, NAD⁺ oxidoreductase) has been identified on a two-dimensional gel (isoelectric focusing-SDS gel) containing up to 150 stained protein spots from a crude Drosophila homogenate. Preliminary identification of the α-GPDH spot was made by including a suitable amount of purified Drosophila α-GPDH in crude fly homogenates prior to electrophoresis and observing an intensity enhancement of the corresponding protein spot on the gels. When three purified electrophoretic variants (slow, fast, and ultrafast) were mixed and analyzed by two-dimensional gel electrophoresis, horizontal displacements of the three protein spots were observed. Immunoprecipitation of the enzyme prior to electrophoresis and gene mapping further confirmed the identity of the α-GPDH protein spot. The α-GPDH spot can also be detected by autoradiography of a two-dimensional gel from a single fly extract, where it has been estimated to constitute 0.5–1% of the total soluble protein. Mutants which express no apparent α-GPDH activity were analyzed by two-dimensional gels and immunoelectrophoresis in an attempt to identify and characterize the inactive proteins. It is suggested that these techniques provide a powerful tool for the analysis of CRM⁺-null activity mutants of a specific gene-enzyme system.     

25OHD, a circulating vitamin D metabolite in fish.

Serum and hepatic 25-hydroxyvitamin D (25OHD), and serum calcium, phosphate, 25OHD₃ binding capacity and binding affinity were measured in male and female trout. Both serum and hepatic 25OHD levels are decreased in female trout with elevations in protein bound calcium and phosphate. Whereas the apparent dissociation constant (Kd) for serum binding of 25OHD₃ of 1.0–2.0 × 10^?9M is similar in males and females, the 25OHD₃ binding capacity of hypercalcemic spawning trout (1.39 × 10^?7M) is significantly less than that of male fish (1.88 × 10^?7M). At circulating serum concentrations of 25OHD which average 9.5 × 10^?9M only 5–7% of trout serum 25OHD binding sites are occupied.     

Critical micelle concentrations of gangliosides

The micellar properties of mixed, bovine gangliosides and purified galactosyl-N-acetylacetylgalactosaminyl (N-acetylneuraminyl) galactosylglucosylceramide were studied by gel filtration, equilibrium dialysis, and band and boundary centrifugation in sucrose gradients. The dissociation of micelles is very slow (days) in water and required us to approach equilibrium by association of monomers rather than by the dissociation of micelles. The gangliosides were therefore first converted into very low molecular weight aggregates (1-3 molecules) by dissolving them in Me2SO. Galactosyl-N-acetylgalactosaminyl(N-acetylneuraminyl)galactosylglucosylceramide was then diluted into aqueous sucrose gradients and sedimented by the boundary centrifugation technique. This gave a sedimenting micelle and a nonsedimenting monomer concentration of (1-2) x 10-10 M (or less) which corresponds to the critical micelle concentration value. The mixed gangliosides revealed two micellar sizes (i.e., 10 and 4.5 S), the slower sedimenting species being formed from the larger one with time (days). The critical micelle concentration of the mixed gangliosides was found to be approximately 10-8 M by a gel filtration, equilibrium dialysis, and band centrifugation.     

Biochemical and immunological studies of three genetic variants of 3-phosphoglycerate kinase 2 from the mouse

Three electrophoretic variants of 3-phosphoglycerate kinase 2 (PGK-2A, PGK-2B, and PGK-2C) were purified from DBA/2J, C3H/HeJ, and C57L/J mice, respectively. PGK-2C exhibits only 2% of the specific activity of PGK-2A and PGK-2B in the reaction leading to the formation of 1,3-diphosphoglycerate. Compared to PGK-2A and PGK-2B, PGK-2C exhibits broader coenzyme specificity and lower K_ms for substrate and coenzymes. Incubation at 45C revealed that PGK-2B is more heat stable than either PGK-2A or PGK-2C. Enzyme immunoinactivation and double immunodiffusion studies showed that mice carrying any one of these three PGK-2 alleles have similar amounts of proteins for PGK-1 and PGK-2 in testes. The results of these studies suggest that low PGK-2C activity in C57L/J mice is a result of a structural rather than a regulatory gene mutation.     

A novel method for converting apolipoprotein B, the major protein moiety of human plasma low density lipoproteins, into a water-soluble protein.

We have developed a new technique to solubilize apolipoprotein B (ApoB) in aqueous solutions. The procedure involves stirring ApoB in 6 M guanidine/20 mM NH4Cl/NH4OH in the presence of cupric ammonia complexes at pH 9.7 for 20 h in N2, and then removing these reagents by a series of dialysis in N2. The resulting Cu(NH3)4(2)+-treated (Cu2+-treated) ApoB is soluble in aqueous buffers of pH above 8.3 or below 3. Parallel experiments carried out on control proteins, human albumin, alpha-lactalbumin, and insulin, indicated no change in molecular weight and no creation of a new NH2-terminal amino acid after Cu2+-treatment. By Edman degradation, the Cu2+-treated ApoB showed no detectable NH2-terminal amino acid. These results showed that the mechanism of Cu2+-solubilization of ApoB was not due to the cleavage of peptide bonds. Electrophoresis on urea-polyacrylamide gel, Cu2+-treated ApoB showed the same number of bands as the non-treated ApoB in the separating gels (7%) near the cathode, suggesting the heterogeneity of ApoB. In SDS-polyacrylamide gel (10%), the reduced and Cu2+-treated ApoB migrated with the similar mobilities to the monomer or dimer of human albumin. Antibodies raised against Cu2+-treated ApoB gave at least two immunoprecipitin lines against the Cu2+-treated ApoB as well as the non-treated guanidine-HCl-soluble ApoB, suggesting the presence of non-identical subunits.     

Production of potent antivenin against cobra venom with conjugated-cobrotoxin.

Cobra venom (Naja naja atra) and its fractions obtained by ammonium sulfate precipitation were subjected to chromatography on CM-Cellulose colum. A highly purified cobrotoxin obtained by the repeated chromatography on preparative CM-Cellulose column was 6.7 times more toxic than the original cobra venom. The toxin was detoxified by a bifunctional reagent, glutaraldehyde, to about 99.8% and utilized for immunization in animals. Mice received 4 weekly immunization with detoxified cobrotoxin and challenged one week after the last injection showed 60% protection in rabbits by immunization with detoxified cobrotoxin reached 360 LD50 neutralizing level against the cobra venom within 30 days. The results indicate that it is feasible and promising to prepare potent antivenin in animals by glutaraldehyde-treated cobrotoxin.     

Macrophage-T cell interactions. III. Production from T cells, under the influence of macrophages, of a factor which complexes Ig and antigen.

Soluble complexes of Ig and antigen have been detected in the serum of mice within 6 hr after immunization. Such complexes are taken up by a subpopulation of T cells. We present evidence which suggests that the complexes are formed through the mediation of a factor released from T cells, tentatively called Ig-antigen complexing factor or IACF. IACF is produced as a result of a macrophage/T-cell interaction, when macrophages are present in an optimal proportion in relation to T cells (4%). Particulate or aggregated substances stimulate macrophages to release a mediator which subsequently acts on Fc receptor-negative T cells to produce IACF. Free-SH groups are important for the activity of the macrophage mediator. Mercaptoethanol and l-cysteine can also release IACF from T cells in the absence of macrophages. Protein synthesis is necessary for the production of this factor, the activity of which is abolished by trypsin digestion. It is postulated that the complexes of Ig and antigen formed under the influence of IACF represent a mechanism of presentation of antigen to T cells.