When DNA Polymerases Multitask: Functions Beyond Nucleotidyl Transfer

DNA polymerases catalyze nucleotidyl transfer, the central reaction in synthesis of DNA polynucleotide chains. They function not only in DNA replication, but also in diverse aspects of DNA repair and recombination. Some DNA polymerases can perform translesion DNA synthesis, facilitating damage tolerance and leading to mutagenesis. In addition to these functions, many DNA polymerases conduct biochemically distinct reactions. This review presents examples of DNA polymerases that carry out nuclease (3ʹ—5′ exonuclease, 5′ nuclease, or end-trimming nuclease) or lyase (5′ dRP lyase) extracurricular activities. The discussion underscores how DNA polymerases have a remarkable ability to manipulate DNA strands, sometimes involving relatively large intramolecular movement.

Pyruvate:ferredoxin oxidoreductase and low abundant ferredoxins support aerobic photomixotrophic growth in cyanobacteria

The decarboxylation of pyruvate is a central reaction in the carbon metabolism of all organisms. Both the pyruvate:ferredoxin oxidoreductase (PFOR) and the pyruvate dehydrogenase (PDH) complex catalyze this reaction. Whereas PFOR reduces ferredoxin, the PDH complex utilizes NAD+. Anaerobes rely on PFOR, which was replaced during evolution by the PDH complex found in aerobes. Cyanobacteria possess both. Our data challenge the view that PFOR is exclusively utilized for fermentation. Instead, we show, that the cyanobacterial PFOR is stable in the presence of oxygen in vitro and is required for optimal photomixotrophic growth under aerobic conditions while the PDH complex is inactivated under the same conditions. We found that cells rely on a general shift from utilizing NAD(H)-dependent to ferredoxin-dependent enzymes under these conditions. The utilization of ferredoxins instead of NAD(H) saves a greater share of the Gibbs free energy, instead of wasting it as heat. This obviously simultaneously decelerates metabolic reactions as they operate closer to their thermodynamic equilibrium. It is common thought that during evolution, ferredoxins were replaced by NAD(P)H due to their higher stability in an oxidizing atmosphere. However, utilization of NAD(P)H could also have been favored due to a higher competitiveness because of an accelerated metabolism.

Biochemical unity revisited: microbial central carbon metabolism holds new discoveries, multi-tasking pathways, and redundancies with a reason

For a long time, our understanding of metabolism has been dominated by the idea of biochemical unity, i.e., that the central reaction sequences in metabolism are universally conserved between all forms of life. However, biochemical research in the last decades has revealed a surprising diversity in the central carbon metabolism of different microorganisms. Here, we will embrace this biochemical diversity and explain how genetic redundancy and functional degeneracy cause the diversity observed in central metabolic pathways, such as glycolysis, autotrophic CO2 fixation, and acetyl-CoA assimilation. We conclude that this diversity is not the exception, but rather the standard in microbiology.

Dynamics of Central and Peripheral Cardiovascular Indices While Performing Repetitive Dosed Exercise Test

Research background and hypothesis. Various physical loads require a different level of activation of various physiological systems and physiological mechanisms, which can highlight the synergetic interaction between central and peripheral mechanisms. Research aim. The aim of this study of this study was to identify and compare the central and peripheral reactions of cardiovascular system while performing repetitive dosed exercise test.Research methods. The participants in the study (15 persons in each of the four groups: non-athletes males; non-athletes females; well-trained endurance runners and well-trained sprinters) performed three Roufier exercise tests, i. e. 30 squats per 45 s with two minutes of rest between exercising. 12-leads ECG was registered and the heart rate (HR), the duration of interval JT were measured and analysed. Changes of oxygen saturation (StO 2 ) in m. vastus leteralis were measured by near-infrared spectroscopy.Research results. One time performance of the physical load may not reveal any central and peripheral synergic peculiarities as adaptation to physical loads in cumulative. For non-athletes the performance of repetitive Roufier tests every two minutes produced the fatigue summation effects which were typical of central and peripheral indices; for well-trained athletes we observed the stability of central reaction and fatigue effects in peripheral responses.Discussion and conclusions. A lot of cardiovascular indices may indicate the summation effects of fatigue while repeatedly performing a Roufier Test with two minutes of rest between exercising. The peripheral changes start first and they impact the central cardiovascular changes.Keywords: electrocardiogram, dosed exercise test, oxygen saturation

Anxiété et Programme D’action

RésuméLes expressions cliniques de l’anxiété sont diverses et assez indépendantes les unes des autres. Les causes sont également diverses, en partie psychologiques et sociales, en partie organiques. La classification nosologique prête à discussion. Comment pouvons-nous maintenir notre intuition forte que l’anxiété est un processus bien particulier au regard de ces données hétérogènes?L’idée que l’anxiété réalise un comportement de peur est commune aux traditions phénoménologique, psychanalytique et behavioriste. Une des raisons de la diversité des données empiriques tient pourtant au fait qu’il n’y a pas de comportement spécifique à l’anxiété.Celle-ci doit être décrite à la fois comme une interruption des plans d’actions du sujet (ce qui est commun a toutes les émotions) et comme l’absence de tout plan d’action qui pourait répondre à la situation (contrairement aux autres émotions).On peut, à partir de là, décrire l’anxiété comme un processus cyclique. A l’occasion d’une interruption primaire de tout programme d’action s’établirait une réponse d’éveil autour du système nerveux autonome (autonomic arousal) et du système nerveux central (réaction d’orientation). Aucune action spécifique ne peut être produite. Il en résulte soit des actions de substitut (phobies, obsessions, agressivité) qui échouent partiellement à arrêter le processus, soit un état de vide cognitif qui entretient le processus d’inhibition. Ce modèle explique la diversité des «entrées» étiologiques et celle des cibles d’action des différentes thérapeutiques.En effet, on peut montrer que l’on entre dans le cycle de l’anxiété par l’une quelconque de ces étapes. De même, les thérapeutiques psychologiques et médicamenteuses agissent sur des processus qui sous-tendent ces étapes.