Commentaries on Viewpoint: Distinct modalities of eccentric exercise: different recipes, not the same dish

International audienc

Effects of a trail running competition on muscular performance and efficiency in well-trained young and master athletes

International audienceTo determine the acute effects of a trail running competition and the age-dependent differences between young and master athletes, 23 subjects [10 young (30.5 ± 7 years), 13 master (45.9 ± 5.9 years)] participated in a 55-km trail running competition. The study was conceived as an intervention study compromising pre, post 1, 24, 48 and 72 h measurements. Measurements consisted of blood tests, ergometer cycling and maximal isometric voluntary contractions (MVC). Parameters monitored included MVC, twitch-and M-wave properties, EMG (RMS) of the vastus lateralis, two locomotion efficiency calculations and muscle damage markers in the blood (CK, LDH). Results indicate post-race increases in CK and LDH, decreases in MVC values (-32 vs.-40% in young and master, P < 0.01), decreases in EMG, increases in contraction time and concomitant decreases in peak twitch values, and a decrease in locomotion efficiency (-4.6 vs.-6.3% in young and master, P < 0.05). Masters showed similar fatigue and muscle damage than young but recuperation was slowed in masters. This study shows that trail runs are detrimental to muscle function, and gives indication that training may not halt muscle deterioration through aging, but can help maintain performance level

Structural basis for the substrate selectivity of Helicobacter pylori NucT nuclease activity

The Phospholipase D (PLD) superfamily of proteins includes a group of enzymes with nuclease activity on various nucleic acid substrates. Here, with the aim of better understanding the substrate specificity determinants in this subfamily, we have characterised the enzymatic activity and the crystal structure of NucT, a nuclease implicated in Helicobacter pylori purine salvage and natural transformation and compared them to those of its bacterial and mammalian homologues. NucT exhibits an endonuclease activity with a strong preference for single stranded nucleic acids substrates. We identified histidine124 as essential for the catalytic activity of the protein. Comparison of the NucT crystal structure at 1.58 angstrom resolution reported here with those of other members of the sub-family suggests that the specificity of NucT for single-stranded nucleic acids is provided by the width of a positively charged groove giving access to the catalytic site

ComFC mediates transport and handling of single-stranded DNA during natural transformation

International audienceAbstract The ComFC protein is essential for natural transformation, a process that plays a major role in the spread of antibiotic resistance genes and virulence factors across bacteria. However, its role remains largely unknown. Here, we show that Helicobacter pylori ComFC is involved in DNA transport through the cell membrane, and is required for the handling of the single-stranded DNA once it is delivered into the cytoplasm. The crystal structure of ComFC includes a zinc-finger motif and a putative phosphoribosyl transferase domain, both necessary for the protein’s in vivo activity. Furthermore, we show that ComFC is a membrane-associated protein with affinity for single-stranded DNA. Our results suggest that ComFC provides the link between the transport of the transforming DNA into the cytoplasm and its handling by the recombination machinery

ComF is a key mediator in single-stranded DNA transport and handling during natural transformation

Natural transformation plays a major role in the spreading of antibiotic resistances and virulence factors. Whilst bacterial species display specificities in the molecular machineries allowing transforming DNA capture and integration into their genome, the ComF(C) protein is essential for natural transformation in all Gram- positive and - negative species studied. Despite this, its role remains largely unknown. Here, we show that Helicobacter pylori ComF is not only involved in DNA transport through the cell membrane, but it also required for the handling of the ssDNA once it is delivered into the cytoplasm. ComF crystal structure revealed the presence of a zinc-finger motif and a putative phosphoribosyl transferase domain, both necessary for its in vivo activity. ComF is a membrane-associated protein with affinity for single-stranded DNA. Collectively, our results suggest that ComF provides the link between the transport of the transforming DNA into the cytoplasm and its handling by the recombination machinery

Dimer of NucT and comparative analysis with PLD family nucleases.

<p><b>(A)</b> Ribbon diagrams of the dimers of NucT, Nuc, Zuc, hBJ-TSA-9 and hFAM83B in two orientations (profile and on top). One monomer is in green and the other on grey. The helices and loops which line the groove of the catalytic pockets are in orange. The extra loops of NucT, hBJ-TSA-9 and hFAM83B are indicated by a pink arrow. <b>(B)</b> Electrostatic surfaces of the top of the dimers. The basic electropositive residues are in blue and the acidic electronegative ones are in red.</p

X-ray structure of the NucT monomer.

<p><b>(A)</b> Structure-based sequence alignment of NucT [25-end], Nuc [24-end] and Zucchini [36–209]. The multialignment was generated by Clustalw2 [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0189049#pone.0189049.ref032" target="_blank">32</a>]. The figure was generated using ESPRIPT [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0189049#pone.0189049.ref033" target="_blank">33</a>]. The secondary structure elements of NucT are in black on the top of the multialignment. The functional residues are pointed by blue stars. The sequence of the extra loop of NucT is boxed in cyan. <b>(B)</b> Structure superimposition of NucT^H124N (cyan) with Nuc (PDB ID 1byr, grey) and Zucchini (PDB ID 4ggk, green). The amino acids involved in the active site are in sticks. The extra loop of NucT is indicated.</p

Data collection and structure refinement statistics.

<p>Data collection and structure refinement statistics.</p