MopA, the Mn Oxidizing Protein From Erythrobacter sp. SD-21, Requires Heme and NAD+ for Mn(II) Oxidation

Bacterial manganese (Mn) oxidation is catalyzed by a diverse group of microbes and can affect the fate of other elements in the environment. Yet, we understand little about the enzymes that catalyze this reaction. The Mn oxidizing protein MopA, from Erythrobacter sp. strain SD-21, is a heme peroxidase capable of Mn(II) oxidation. Unlike Mn oxidizing multicopper oxidase enzymes, an understanding of MopA is very limited. Sequence analysis indicates that MopA contains an N-terminal heme peroxidase domain and a C-terminal calcium binding domain. Heterologous expression and nickel affinity chromatography purification of the N-terminal peroxidase domain (MopA-hp) from Erythrobacter sp. strain SD-21 led to partial purification. MopA-hp is a heme binding protein that requires heme, NAD+, and calcium (Ca2+) for activity. Mn oxidation is also stimulated by the presence of pyrroloquinoline quinone. MopA-hp has a KM for Mn(II) of 154 ± 46 μM and kcat = 1.6 min−1. Although oxygen requiring MopA-hp is homologous to peroxidases based on sequence, addition of hydrogen peroxide and hydrogen peroxide scavengers had little effect on Mn oxidation, suggesting this is not the oxidizing agent. These studies provide insight into the mechanism by which MopA oxidizes Mn

The impact of an acute bout of high intensity exercise on corticospinal excitability and transcallosal inhibition in older adults

While studies have investigated the effect of exercise on corticospinal, intracortical, and interhemispheric processes in young adults, few studies have focused on older adults. Current evidence supports the hypothesis that there is a shift from predominantly inhibitory to excitatory interhemispheric interactions as we age. Other work suggests that changes observed in transcallosal inhibition (TCI) with age (i.e., reduced ipsilateral silent period (iSP) duration and area) may be mitigated by physical activity. Therefore, the main purpose of this experiment was to advance understanding of how an acute bout of high intensity exercise alters patterns of corticospinal and interhemispheric excitability in the healthy older adult population. 41 healthy older adults participated in this study. Participants were randomized into the exercise (n=21) or the rest (n=20) group. Participants in the exercise group completed an acute bout of high intensity exercise on a recumbent bike lasting 23 minutes. Participants in the rest group sat for the same duration of time while their attention was controlled by watching a nature documentary. Corticospinal excitability and TCI of the upper limbs was assessed via transcranial magnetic stimulation before (baseline), immediately (Post 1), and 30 minutes (Post 2) following high intensity exercise or rest. Results indicated that there was an increase in corticospinal excitability immediately and 30 minutes post exercise in the dominant hemisphere. There was also an interaction effect between timepoint and hemisphere in transcallosal inhibition. The current study showed following an acute bout of high intensity exercise, there was an increase in corticospinal excitability in the dominant hemisphere and a hemispheric difference in TCI in older adults. The present research provides insight on how exercise could be used to mitigate age related changes in the brain and informs how exercise therapies could be employed in association with rehabilitation in clinical populations.Medicine, Faculty ofPhysical Therapy, Department ofGraduat

\u3ci\u3eDrosophila\u3c/i\u3e Muller F Elements Maintain a Distinct Set of Genomic Properties Over 40 Million Years of Evolution

The Muller F element (4.2 Mb, ~80 protein-coding genes) is an unusual autosome of Drosophila melanogaster; it is mostly heterochromatic with a low recombination rate. To investigate how these properties impact the evolution of repeats and genes, we manually improved the sequence and annotated the genes on the D. erecta, D. mojavensis, and D. grimshawi F elements and euchromatic domains from the Muller D element. We find that F elements have greater transposon density (25–50%) than euchromatic reference regions (3–11%). Among the F elements, D. grimshawi has the lowest transposon density (particularly DINE-1: 2% vs. 11–27%). F element genes have larger coding spans, more coding exons, larger introns, and lower codon bias. Comparison of the Effective Number of Codons with the Codon Adaptation Index shows that, in contrast to the other species, codon bias in D. grimshawi F element genes can be attributed primarily to selection instead of mutational biases, suggesting that density and types of transposons affect the degree of local heterochromatin formation. F element genes have lower estimated DNA melting temperatures than D element genes, potentially facilitating transcription through heterochromatin. Most F element genes (~90%) have remained on that element, but the F element has smaller syntenic blocks than genome averages (3.4–3.6 vs. 8.4–8.8 genes per block), indicating greater rates of inversion despite lower rates of recombination. Overall, the F element has maintained characteristics that are distinct from other autosomes in the Drosophila lineage, illuminating the constraints imposed by a heterochromatic milieu