Proton transfer from the bulk to the bound ubiquinone Q(B) of the reaction center in chromatophores of Rhodobacter sphaeroides: retarded conveyance by neutral water

The mechanism of proton transfer from the bulk into the membrane protein interior was studied. The light-induced reduction of a bound ubiquinone molecule Q(B) by the photosynthetic reaction center is accompanied by proton trapping. We used kinetic spectroscopy to measure (i) the electron transfer to Q(B) (at 450 nm), (ii) the electrogenic proton delivery from the surface to the Q(B) site (by electrochromic carotenoid response at 524 nm), and (iii) the disappearance of protons from the bulk solution (by pH indicators). The electron transfer to Q(B)(-) and the proton-related electrogenesis proceeded with the same time constant of approximately 100 microseconds (at pH 6.2), whereas the alkalinization in the bulk was distinctly delayed (tau approximately 400 microseconds). We investigated the latter reaction as a function of the pH indicator concentration, the added pH buffers, and the temperature. The results led us to the following conclusions: (i) proton transfer from the surface-located acidic groups into the Q(B) site followed the reduction of Q(B) without measurable delay; (ii) the reprotonation of these surface groups by pH indicators and hydronium ions was impeded, supposedly, because of their slow diffusion in the surface water layer; and (iii) as a result, the protons were slowly donated by neutral water to refill the proton vacancies at the surface. It is conceivable that the same mechanism accounts for the delayed relaxation of the surface pH changes into the bulk observed previously with bacteriorhodopsin membranes and thylakoids. Concerning the coupling between proton pumps in bioenergetic membranes, our results imply a tendency for the transient confinement of protons at the membrane surface.     

Molecular mechanisms of retroviral integrase inhibition and the evolution of viral resistance

The development of HIV integrase (IN) strand transfer inhibitors (INSTIs) and our understanding of viral resistance to these molecules have been hampered by a paucity of available structural data. We recently reported cocrystal structures of the prototype foamy virus (PFV) intasome with raltegravir and elvitegravir, establishing the general INSTI binding mode. We now present an expanded set of cocrystal structures containing PFV intasomes complexed with first- and second-generation INSTIs at resolutions of up to 2.5 ?. Importantly, the improved resolution allowed us to refine the complete coordination spheres of the catalytic metal cations within the INSTI-bound intasome active site. We show that like the Q148H/G140S and N155H HIV-1 IN variants, the analogous S217H and N224H PFV INs display reduced sensitivity to raltegravir in vitro. Crystal structures of the mutant PFV intasomes in INSTI-free and -bound forms revealed that the amino acid substitutions necessitate considerable conformational rearrangements within the IN active site to accommodate an INSTI, thus explaining their adverse effects on raltegravir antiviral activity. Furthermore, our structures predict physical proximity and an interaction between HIV-1 IN mutant residues His148 and Ser/Ala140, rationalizing the coevolution of Q148H and G140S/A mutations in drug-resistant viral strains.     

Penetrating cation/fatty acid anion pair as a mitochondria-targeted protonophore

A unique phenomenon of mitochondria-targeted protonophores is described. It consists in a transmembrane H⁺-conducting fatty acid cycling mediated by penetrating cations such as 10-(6’-plastoquinonyl)decyltriphenylphosphonium (SkQ1) or dodecyltriphenylphosphonium (C₁₂TPP). The phenomenon has been modeled by molecular dynamics and directly proved by experiments on bilayer planar phospholipid membrane, liposomes, isolated mitochondria, and yeast cells. In bilayer planar phospholipid membrane, the concerted action of penetrating cations and fatty acids is found to result in conversion of a pH gradient (ΔpH) to a membrane potential (Δψ) of the Nernstian value (about 60 mV Δψ at ΔpH = 1). A hydrophobic cation with localized charge (cetyltrimethylammonium) failed to substitute for hydrophobic cations with delocalized charge. In isolated mitochondria, SkQ1 and C₁₂TPP, but not cetyltrimethylammonium, potentiated fatty acid-induced (i) uncoupling of respiration and phosphorylation, and (ii) inhibition of H₂O₂ formation. In intact yeast cells, C₁₂TPP stimulated respiration regardless of the extracellular pH value, whereas a nontargeted protonophorous uncoupler (trifluoromethoxycarbonylcyanide phenylhydrazone) stimulated respiration at pH 5 but not at pH 3. Hydrophobic penetrating cations might be promising to treat obesity, senescence, and some kinds of cancer that require mitochondrial hyperpolarization.     

Modified laparoscopic fundoplication in the treatment of gastroesophageal reflux

The results of laparoscopic fundoplication in patients with the gastroesophageal reflux disease are described. Operations were performed by the classical Dor method (19 patients) and by a modified method (35 patients). An analysis of results of the operation has shown effectiveness and safety of using the modified method of laparoscopic fundoplication.     

Oral Supplementation with L-Carnosine Attenuates Social Recognition Deficits in CD157KO Mice via Oxytocin Release

The outcomes of supplementation with L-carnosine have been investigated in clinical trials in children with autism spectrum disorder (ASD). However, reports on the effects of L-carnosine in humans have been inconsistent, and the efficacy of L-carnosine supplementation for improving ASD symptoms has yet to be investigated in animal studies. Here, we examined the effects of oral supplementation with L-carnosine on social deficits in CD157KO mice, a murine model of ASD. Social deficits in CD157KO mice were assessed using a three-chamber social approach test. Oral supplementation with L-carnosine attenuated social behavioral deficits. The number of c-Fos-positive oxytocin neurons in the supraoptic nucleus and paraventricular nucleus was increased with L-carnosine supplementation in CD157KO mice after the three-chamber social approach test. We observed an increase in the number of c-Fos-positive neurons in the basolateral amygdala, a brain region involved in social behavior. Although the expression of oxytocin and oxytocin receptors in the hypothalamus was not altered by L-carnosine supplementation, the concentration of oxytocin in cerebrospinal fluid was increased in CD157KO mice by L-carnosine supplementation. These results suggest that L-carnosine supplementation restores social recognition impairments by augmenting the level of released oxytocin. Thus, we could imply the possibility of a safe nutritional intervention for at least some types of ASD in the human population.     

Reading the signs of starvation

Guidelines for managing malnutrition in adolescent eating disorders are based on limited evidence. Swenne and Engström's study explored the relationship between symptoms, signs and weight status in this patient group, towards refining clinical approaches to nutritional assessment in adolescents. Conclusion: The need to compare findings across studies is crucial for research in nutritional assessment of adolescents.