CYP116B5: a new class VII catalytically self‐sufficient cytochrome P450 from Acinetobacter radioresistens that enables growth on alkanes

A gene coding for a class VII cytochrome P450 monooxygenase (CYP116B5) was identified from Acinetobacter radioresistens S13 growing on media with medium (C14, C16) and long (C24, C36) chain alkanes as the sole energy source. Phylogenetic analysis of its N‐ and C‐terminal domains suggests an evolutionary model involving a plasmid‐mediated horizontal gene transfer from the donor Rhodococcus jostii RHA1 to the receiving A. radioresistens S13. This event was followed by fusion and integration of the new gene in A. radioresistens chromosome. Heterologous expression of CYP116B5 in Escherichia coli BL21, together with the A. radioresistens Baeyer–Villiger monooxygenase, allowed the recombinant bacteria to grow on long‐ and medium‐chain alkanes, showing that CYP116B5 is involved in the first step of terminal oxidation of medium‐chain alkanes overlapping AlkB and in the first step of sub‐terminal oxidation of long‐chain alkanes. It was also demonstrated that CYP116B5 is a self‐sufficient cytochrome P450 consisting of a heme domain (aa 1–392) involved in the oxidation step of n‐alkanes degradation, and its reductase domain (aa 444–758) comprising the NADPH‐, FMN‐ and [2Fe2S]‐binding sites. To our knowledge, CYP116B5 is the first member of this class to have its natural substrate and function identified.     

Abscisic Acid Transport in Human Erythrocytes

Abscisic acid (ABA) is a plant hormone involved in the response to environmental stress. Recently, ABA has been shown to be present and active also in mammals, where it stimulates the functional activity of innate immune cells, of mesenchymal and hemopoietic stem cells, and insulin-releasing pancreatic β-cells. LANCL2, the ABA receptor in mammalian cells, is a peripheral membrane protein that localizes at the intracellular side of the plasma membrane. Here we investigated the mechanism enabling ABA transport across the plasmamembrane of human red blood cells (RBC). Both influx and efflux of [³H]ABA occur across intact RBC, as detected by radiometric and chromatographic methods. ABA binds specifically to Band 3 (the RBC anion transporter), as determined by labeling of RBC membranes with biotinylated ABA. Proteoliposomes reconstituted with human purified Band 3 transport [³H]ABA and [³⁵S]sulfate, and ABA transport is sensitive to the specific Band 3 inhibitor 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid. Once inside RBC, ABA stimulates ATP release through the LANCL2-mediated activation of adenylate cyclase. As ATP released from RBC is known to exert a vasodilator response, these results suggest a role for plasma ABA in the regulation of vascular tone.     

Stimulus-driven orienting of visuo-spatial attention in complex dynamic environments

In everyday life attention operates within complex and dynamic environments, while laboratory paradigms typically employ simple and stereotyped stimuli. This fMRI study investigated stimulus-driven spatial attention using a virtual-environment video. We explored the influence of bottom-up signals by computing saliency maps of the environment and by introducing attention-grabbing events in the video. We parameterized the efficacy of these signals for the orienting of spatial attention by measuring eye movements and used these parameters to analyze the imaging data. The efficacy of bottom-up signals modulated ongoing activity in dorsal fronto-parietal regions and transient activation of the ventral attention system. Our results demonstrate that the combination of computational, behavioral, and imaging techniques enables studying cognitive functions in ecologically valid contexts. We highlight the central role of the efficacy of stimulus-driven signals in both dorsal and ventral attention systems, with a dissociation of the efficacy of background salience versus distinctive events in the two systems.