Oxidative and reductive reactions of sulphhaemoglobin with various reagents correlated with changes in quaternary structure of the protein.

The absorption maxima in the Soret region and near 620nm of sulphhaemoglobin shifted from 419.5nm to 423nm and from 623nm to 619nm respectively with a decrease in oxygen concentrations of the sulphhaemoglobin solution [101.3, 20.3 and 0 kPa (760, 152 and 0 mmHg) partial pressures]. The major changes in the positions of the absorption maxima occurred drastically at oxygen concentrations between 20.3 kPa and 0 kPa, suggesting that the quaternary structure of sulphhaemoglobin has changed from the R to the T state. Inositol hexaphosphate, a known allosteric effector of haemoglobin, enhanced the shift in peak location. This result supports the view that the shift of the absorption maxima reflects changes in the conformation of sulphhaemoglobin. To investigate the relationship between the conformation of sulphhaemoglobin and the reactivity of the protein with various reagents, we studied the oxidation and reduction reactions of the protein with ascorbic acid, ferricyanide and nitrite under aerobic and anaerobic conditions. The results showed that the rates of oxidation and reduction of ferrous and ferric sulphhaemoglobins with these compounds are associated with the conformation of the protein.     

Involvement of oxidoreductive reactions of intracellular haemoglobin in the metabolism of 3-hydroxyanthranilic acid in human erythrocytes.

3-Hydroxyanthranilic acid, a metabolite of tryptophan, was rapidly metabolized by human erythrocytes. The final product was determined to be cinnabarinic acid as detected by spectrophotometry, paper chromatography and t.l.c. The formation of cinnabarinic acid from 3-hydroxyanthranilic acid in the cells was markedly inhibited by CO when intracellular haemoglobin was in a ferrous state, and by cyanide when it was in a ferric state. Ferrous haemoglobin in erythrocytes was oxidized to (alpha 3+ beta 2+)2, (alpha 2+ beta 3+)2 and (alpha 3+ beta 3+)2 by 3-hydroxyanthranilic acid, and the oxidation rates were very high, like those of cinnabarinic acid formation, suggesting that the metabolism of 3-hydroxyanthranilic acid is coupled with oxidoreductive reactions of intracellular haemoglobin. This view was further confirmed by the findings that 3-hydroxyanthranilic acid was metabolized by ferrous or ferric haemoglobin and that ferrous and ferric haemoglobins were oxidized and reduced by the compound respectively. The significance of the metabolism of 3-hydroxyanthranilic acid and the oxidoreductive reactions of haemoglobin with this compound may be associated with the pathological conditions with increased 3-hydroxyanthranilic acid levels in the blood of diabetic subjects.     

Variations of Natural 15N Abundances in Leguminous Plants and Nodule Fractions

Natural ¹⁵N abundances of various tissues from twelve speciesof leguminous plants and those of nodule fractions from threespecies grown in Japan were determined by mass spectrometry.The ¹⁵N concentrations of non-nodular tissues of nodulated plantswere close to the value of atmospheric N₂. The nodules of soybean,mung bean, cowpea, kidney bean, adzuki bean, sword bean, whiteclover, Leucaena leucocephala, and horsegram showed highly elevated¹⁵N concentrations, and those of pea had a slightly enriched¹⁵N concentration compared to other tissue, while the nodulesof peanut and lucerne had ¹⁵N values similar to those of theirshoot tissues. The bacteroid fractions from horsegram, swordbean and peanut had higher ¹⁵N concentrations than the cytosolfractions. (Received March 17, 1984; Accepted August 21, 1984)     

Fecal microbiota transplantation prevents Candida albicans from colonizing the gastrointestinal tract

Gut microbes symbiotically colonize the gastrointestinal (GI) tract, interacting with each other and their host to maintain GI tract homeostasis. Recent reports have shown that gut microbes help protect the gut from colonization by pathogenic microbes. Here, we report that commensal microbes prevent colonization of the GI tract by the pathogenic fungus, Candida albicans. Wild‐type specific pathogen‐free (SPF) mice are resistant to C. albicans colonization of the GI tract. However, administering certain antibiotics to SPF mice enables C. albicans colonization. Quantitative kinetics of commensal bacteria are inversely correlated with the number of C. albicans in the gut. Here, we provide further evidence that transplantation of fecal microbiota is effective in preventing Candida colonization of the GI tract. These data demonstrate the importance of commensal bacteria as a barrier for the GI tract surface and highlight the potential clinical applications of commensal bacteria in preventing pathogenic fungal infections.     

In vitro assembly of the functional porin trimer from dissociated monomers in Pseudomonas aeruginosa

The molecular weights of monomeric and oligomeric forms of the newly identified porins, protein D2, of the outer membrane of Pseudomonas aeruginosa appeared to be 47,000 and 137,000, respectively, as determined by the light scattering technique. Presence of the trimeric aggregates of the homologous subunits in the intact outer membrane, the liposome membrane, and the non-ionic surfactant were confirmed through cross-linking experiments and immunoblotting techniques. The protein D2 monomers prepared in 0.1% of sodium dodecyl sulfate at 23 degrees C spontaneously reassembled into the trimeric aggregate when the surfactant dropped below critical concentration. The diffusion rates of saccharides and beta-lactam antibiotics through the liposome membranes reconstituted from the reassembled protein D2 trimers were indistinguishable from those of the native protein D2. This study shed some light on the porin trimer assembly as well as on the mechanism of carbapenem diffusion through the protein D2 pores.     

How do nitrogen and phosphorus deficiencies affect strigolactone production and exudation?

Plants exude strigolactones (SLs) to attract symbiotic arbuscular mycorrhizal fungi in the rhizosphere. Previous studies have demonstrated that phosphorus (P) deficiency, but not nitrogen (N) deficiency, significantly promotes SL exudation in red clover, while in sorghum not only P deficiency but also N deficiency enhances SL exudation. There are differences between plant species in SL exudation under P- and N-deficient conditions, which may possibly be related to differences between legumes and non-legumes. To investigate this possibility in detail, the effects of N and P deficiencies on SL exudation were examined in Fabaceae (alfalfa and Chinese milk vetch), Asteraceae (marigold and lettuce), Solanaceae (tomato), and Poaceae (wheat) plants. In alfalfa as expected, and unexpectedly in tomato, only P deficiency promoted SL exudation. In contrast, in Chinese milk vetch, a leguminous plant, and in the other non-leguminous plants examined, N deficiency as well as P deficiency enhanced SL exudation. Distinct reductions in shoot P levels were observed in plants grown under N deficiency, except for tomato, in which shoot P level was increased by N starvation, suggesting that the P status of the shoot regulates SL exudation. There seems to be a correlation between shoot P levels and SL exudation across the species/families investigated.