Characterization of the consequences of YidC depletion on the inner membrane proteome of E. coli using 2D blue native/SDS-PAGE

In the bacterium Escherichia coli, the essential inner membrane protein (IMP) YidC assists in the biogenesis of IMPs and IMP complexes. Our current ideas about the function of YidC are based on targeted approaches using only a handful of model IMPs. Proteome-wide approaches are required to further our understanding of the significance of YidC and to find new YidC substrates. Here, using two-dimensional blue native/SDS-PAGE methodology that is suitable for comparative analysis, we have characterized the consequences of YidC depletion for the steady-state levels and oligomeric state of the constituents of the inner membrane proteome. Our analysis showed that (i) YidC depletion reduces the levels of a variety of complexes without changing their composition, (ii) the levels of IMPs containing only soluble domains smaller than 100 amino acids are likely to be reduced upon YidC depletion, whereas the levels of IMPs with at least one soluble domain larger than 100 amino acids do not, and (iii) the levels of a number of proteins with established or putative chaperone activity (HflC, HflK, PpiD, OppA, GroEL and DnaK) are strongly increased in the inner membrane fraction upon YidC depletion. In the absence of YidC, these proteins may assist the folding of sizeable soluble domains of IMPs, thereby supporting their folding and oligomeric assembly. In conclusion, our analysis identifies many new IMPs/IMP complexes that depend on YidC for their biogenesis, responses that accompany depletion of YidC and an IMP characteristic that is associated with YidC dependence.     

The regulatory subunit ε in Escherichia coli FOF1-ATP synthase

F-type ATP synthases are extraordinary multisubunit proteins that operate as nanomotors. The Escherichia coli (E. coli) enzyme uses the proton motive force (pmf) across the bacterial plasma membrane to drive rotation of the central rotor subunits within a stator subunit complex. Through this mechanical rotation, the rotor coordinates three nucleotide binding sites that sequentially catalyze the synthesis of ATP. Moreover, the enzyme can hydrolyze ATP to turn the rotor in the opposite direction and generate pmf. The direction of net catalysis, i.e. synthesis or hydrolysis of ATP, depends on the cell's bioenergetic conditions. Different control mechanisms have been found for ATP synthases in mitochondria, chloroplasts and bacteria. This review discusses the auto-inhibitory behavior of subunit ε found in F_OF₁-ATP synthases of many bacteria. We focus on E. coli F_OF₁-ATP synthase, with insights into the regulatory mechanism of subunit ε arising from structural and biochemical studies complemented by single-molecule microscopy experiments.     

Mirrors,monkeys, and group dynamics

When presented with his/her own reflection in a mirror (within an environment that is natural for that particular group of primates) the position that animal holds within the group affects his/her interpretation of that image. Each individual perceives the animal in the mirror to be another animal of equal circumstances as him/herself. An alpha animal sees a potential alpha animal attempting to take over the troop. A beta or lesser animal sees another non-alpha animal attempting to enter the troop through affiliation. In this study a group of zoo raised Japanese macaques were challenged with their own reflection in a mirror. Incidents of aggressive behavior rose in the alpha animals while all affiliative behavior ceased between members of the group. The lesser animals vied for time with the mirror, each attempting to be near the perceived con-specific.     

Pathways of energy conservation in methanogenic archaea

Methanogenic archaea are strictly anaerobic organisms that derive their metabolic energy from the conversion of a restricted number of substrates to methane. H₂+CO₂ and formate are converted to CH₄ via the CO₂-reducing pathway, while methanol and methylamines are metabolized by the methylotrophic pathway. A limited number of methanogenic organisms utilize acetate by the aceticlastic pathway. Redox reactions involved in these processes are partly catalyzed by membrane-bound enzyme systems that generate or, in the case of endergonic reactions, use electrochemical ion gradients. The H₂:heterodisulfide oxidoreductase, the F₄₂₀H₂:heterodisulfide oxidoreductase and the CO:heterodisulfide oxidoreductase, are novel systems that generate a proton motive force by redox-potential-driven H⁺ translocation. The methyltetrahydromethanopterin:coenzyme M methyltransferase is a unique, reversible sodium ion pump that couples methyl transfer with the transport of Na⁺ across the cytoplasmic membrane. Formylmethanofuran dehydrogenase is a reversible ion pump that catalyzes formylation and deformylation, of methanofuran. In summary, the pathways are coupled to the generation of an electrochemical sodium ion gradient and an electrochemical proton gradient. Both ion gradients are used directly for ATP synthesis via membrane integral ATP synthases. The function of the above-mentioned systems and their components in the metabolism of methanogens are described in detail.Abbreviations DCCD N,N dicyclohexylcarbodiimide - F ₄₂₀ (N-l-Lactyl--l-glutamyl)-l-glutamic acid phosphodiester of 7,8 didemethyl-8-hydroxy-5-deazariboflavin-5-phosphate - H ₄MPT Tetrahydromethanopterin - HS-CoM 2-Mercaptoethanesulfonate - HS-HTP 7-Mercaptoheptanoyl-O-phospho-l-threonine - MF Methanofuran - Ms Methanosarcina - Mc Methanococcus - Mb Methanobacterium - SF 6847 3,5-Di-tert-butyl-4-hydroxybenzylidene-malononitrile - Electrochemical sodium ion gradient - Electrochemical proton gradient     

Non-PTS uptake and subsequent metabolism of glucose in Pediococcus halophilus as demonstrated with a double mutant defective in phosphoenolpyruvate:mannose phosphotransferase system and in phosphofructokinase

Pediococcus halophilus possesses phosphoenolpyruvate:mannose phosphotransferase system (man:PTS) as a main glucose transporter. A man:PTS defective (man:PTS^d) strain X-160 could, however, utilize glucose. A possible glucose-transport mechanism other than PTS was studied with the strain X-160 and its derivative, man:PTS^d phosphofructokinase defective (PFK^–) strain M-13. Glucose uptake by X-160 at pH 5.5 was inhibited by any of carbonylcyanide m-chlorophenylhydrazone, nigericin, N,N-dicyclohexylcarbodiimide, or iodoacetic acid. The double mutant M-13 could still transport glucose and accumulated intracellularly a large amount of hexose-phosphates (ca. 8 mM glucose 6-phosphate and ca. 2 mM fructose 6-phosphate). Protonophores also inhibited the glucose transport at pH 5.5, as determined by the amounts of accumulated hexose-phosphates (< 4 mM). These showed involvement of proton motive force (P) in the non-PTS glucose transport. It was concluded that the non-PTS glucose transporter operated in concert with hexokinase or glucokinase for the metabolism of glucose in the man:PTS^d strain.Abbreviations BM basal medium - BM-G basal medium containing glucose - CM complex medium - man:PTS phosphoenolpyruvate:mannose phosphotransferase system - CCCP carbonylcyanide m-chlorophenylhydrazone - DCCD N,N-dicyclohexyl carbodiimide - P proton motive force - pH transmembrane pH gradient - transmembrane electrical potential difference - MNNG N-methyl-N-nitro-N-nitrosoguanidine - PIPES piperazine-N,N-bis(-ethanesulfonic acid) - MES 4-morpholineethanesulfonic acid - G-6-P glucose 6-phosphate - F-6-P fructose 6-phosphate - FDP fructose 1,6-bisphosphate - EMP Embden-Meyerhof-Parnas pathway - PFK phosphofructokinase - GK glucokinase - HK hexokinase - IAA iodoacetic acid - II^man enzyme II component of man:PTS     

Thyroid hormone effects on the State IV proton motive force in rat liver mitochondria

In order to further investigate the mechanisms regulating the control of mitochondrial respiration by thyroid hormone, the proton motive force was measured during State IV respiration in liver mitochondria isolated from euthyroid, hyperthyroid, hypothyroid and T₃-treated hypothyroid rats. The proton motive force was significantly higher in the hyperthyroid group due to an increased pH. The proton motive force of hypothyroid mitochondria was lower than controls due to a decreased membrane potential. The proton motive force for the T3-treated hypothyroid group did not differ from the euthyroid group due to negating changes in the pH gradient and the membrane potential. The intramitochondrial volume was decreased in the hyperthyroid group and unchanged in the other groups. The results indicate that the thyroid status alters the proton motive force in State IV through individual changes in the pH and membrane potential components of the force. The component that changes in hyperthyroid mitochondria is different from that changing in hypothyroid mitochondria.     

Aggression, dominance, and affiliation: Their relationships with androgen levels and intelligence in 5-year-old children

This study explores the potential relationship between social behavior (aggression, dominance, and affiliation) and testosterone, androstenedione, and DHEA measurements in 5-year-old children while also analyzing the moderating effect of IQ on the hormone-behavior relationship. 129 healthy normal Iberian children (60 boys and 69 girls) were videotaped in free play interactions in the school playground. Their behavior was then evaluated with particular emphasis on aggression, government, and affiliation. Testosterone, androstenedione, and DHEA levels were measured using an enzyme immunoassay technique in saliva samples. A test (K-BIT) which provides an IQ measurement for children was also administered to subjects. The correlation analysis revealed a positive relationship between the behavioral factor of Provocation and androstenedione in boys, and a regression analysis indicated that this relationship was moderated in a positive direction by the subject's intelligence. In girls, we observed a positive relationship between testosterone and Affectivity, with this relationship being moderated in a negative direction by intelligence.     

Male–immature interactions seem to depend on group composition in white-headed langur (Trachypithecus leucocephalus)

In primates, male–immature interactions are always multifacetted. We studied male–immature interactions of white-headed langur during our long-term study in Nongguan White-Headed Langur Reserve, Guangxi, China. Male–immature interactions obviously differed between one-male groups and male–immature groups. In one-male groups, adult males behaved tolerantly or aggressively towards immatures and never carried out sociopositive behaviors. Sexual selection theory supports this phenomenon because males are predicted to bias to compete for more mating chances but not to invest in any single offspring. In male–immature groups, however, adult males carried out sociopositive behaviors and never behaved aggressively towards immatures. This is supported by kin selection theory because it will be beneficial for the males to increase the survival of the immatures if they are likely the fathers of them. Thus, we conclude that male–immature interactions differ between one-male groups and male–immature groups because the mating status of males are different between the two kinds of groups.     

Iron transport in Francisella in the absence of a recognizable TonB protein still requires energy generated by the proton motive force

The mechanism of iron transport in Francisella is still a puzzle since none of the sequenced Francisella strains appears to encode a TonB protein, the energy transducer of the proton motive force necessary to act on the bacterial outer membrane siderophore receptor to allow the internalization of iron. In this work we demonstrate using kinetic experiments of radioactive Fe³⁺ utilization, that iron uptake in Francisella novicida, although with no recognizable TonB protein, is indeed dependent on energy generated by the proton motive force. Moreover, mutants of a predicted outer membrane receptor still transport iron and are sensitive to the iron dependent antimicrobial compound streptonigrin. Our studies suggest that alternative pathways to internalize iron might exist in Francisella.