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Nar1 is an essential eukaryotic protein proposed to function as an iron-sulfur (Fe/S) cluster trafficking factor in the cytosolic iron-sulfur assembly (CIA) machinery. However, such a role has remained unclear due to difficulties in purifying adequate amounts of cofactor-bound protein. The [FeFe]-hydrogenase-like protein has two conserved binding sites for [4Fe-4S] clusters, one of which is predicted to be a labile site for cluster transfer to downstream targets. Here, we report a new preparation procedure for Nar1 that facilitated studies by UV-Vis, EPR, and Mössbauer spectroscopies, along with native mass spectrometry. Nar1 recombinantly produced in E. coli contained a [4Fe-4S] cluster, bound presumably at site 1, along with an unexpected [2Fe-2S] cluster bound at an unknown site. Fe/S reconstitution reactions installed a second [4Fe-4S] cluster at site 2, leading to protein with three Fe/S cofactors. Strikingly, one [4Fe-4S] cluster was rapidly destroyed by molecular oxygen, potentially linking Nar1 oxygen sensitivity to phenotypes observed previously in vivo. These advances now allow for the pursuit of in vitro Fe/S cluster transfer assays, which will shed light on Fe/S trafficking by CIA components and how they may facilitate the insertion of [4Fe-4S] and potentially [2Fe-2S] clusters into target proteins in the cytosol.
Nar1 is an essential eukaryotic protein proposed to function as an iron–sulphur (Fe/S) cluster trafficking factor in the cytosolic iron–sulphur protein assembly (CIA) machinery. However, such a role has remained unclear due to difficulties in purifying adequate amounts of cofactor-bound protein. The [FeFe]-hydrogenase-like protein has two conserved binding sites for [4Fe–4S] clusters but does not show hydrogenase activity in vivo due to the lack of an active site [2Fe]H cofactor. Here, we report a new preparation procedure for Nar1 that facilitated studies by UV-vis, EPR, and Mössbauer spectroscopies, along with native mass spectrometry. Nar1 recombinantly produced in E. coli contained a [4Fe–4S] cluster, bound presumably at site 1, along with an unexpected [2Fe–2S] cluster bound at an unknown site. Fe/S reconstitution reactions installed a second [4Fe–4S] cluster at site 2, leading to protein with up to three Fe/S cofactors. It is proposed that the [2Fe–2S] cluster occupies a cavity in Nar1 that is filled by the [2Fe]H cofactor in [FeFe]-hydrogenases. Strikingly, two of the Fe/S clusters were rapidly destroyed by molecular oxygen, linking Nar1 oxygen sensitivity in vitro to phenotypes observed previously in vivo. Our biochemical results, therefore, validate a direct link between cellular oxygen concentrations and the functioning of the CIA pathway. These advances also now allow for the pursuit of in vitro Fe/S cluster transfer assays, which will shed light on Fe/S trafficking and insertion by CIA components.
In the present study, the bivalve Scrobicularia plana, collected from two contrasting areas (pristine location and mercury contaminated area), was selected to assess the biochemical alterations imposed by pH decrease, carbamazepine (an antiepileptic) and the combined effect of both stressors. The effects on oxidative stress related biomarkers after 96 h exposure revealed that pH decrease and carbamazepine induced alterations on clams, with greater impacts on individuals from the contaminated area which presented higher mortality, higher lipid peroxidation and higher glutathione S-transferase activity. These results emphasize the risk of extrapolating results from one area to another, since the same species inhabiting different areas may be affected differently when exposed to the same stressors. Furthermore, the results obtained showed that, when combined, the impact of pH decrease and carbamazepine was lower than each stressor acting alone, which could be related to the defence mechanism of valves closure when bivalves are under higher stressful conditions.
Ocean acidification and increasing discharges of pharmaceutical contaminants into aquatic systems are among key and/or emerging drivers of environmental change affecting marine ecosystems. A growing body of evidence demonstrates that ocean acidification can have direct and indirect impacts on marine organisms although combined effects with other stressors, namely with pharmaceuticals, have received very little attention to date. The present study aimed to evaluate the impacts of the pharmaceutical drug Carbamazepine and pH 7.1, acting alone and in combination, on the clamScrobicularia plana. For this, a long-termexposure (28 days)was conducted and a set of oxidative stress markers was investigated. The results obtained showed that S. plana was able to develop mechanisms to prevent oxidative damage when under low pH for a long period, presenting higher survival when exposed to this stressor compared to CBZ or the combination of CBZ with pH 7.1. Furthermore, the toxicity of CBZ on S. plana was synergistically increased under ocean acidification conditions (CBZ + pH 7.1): specimens survival was reduced and oxidative stress was enhanced when compared to single exposures. These findings add to the growing body of evidence that ocean acidification will act to increase the toxicity of CBZ to marine organisms,which has clear implications for coastal benthic ecosystems suffering chronic pollution from pharmaceutical drugs.
Reported here is the production of molecularly imprinted polymer (MIP) films, integrating a fluorescent moiety that serves as both an element for template interaction and signalling, for the thermal and optical detection of the beta-lactam antibiotic nafcillin. Fluorescein methacrylate (FluMa) was synthesized and introduced during the molecular imprinting process as the sole monomer and in a 1 : 1 mixture with methacrylic acid (MAA), allowing to draw first conclusions on the MIP formation potential of such a rather large and rigid monomer. At first, MIP microparticles containing FluMa were prepared by free radical polymerisation. Optical batch rebinding experiments revealed that FluMa can act as a functional monomer for selective detection of nafcillin; however, the addition of MAA as co-monomer significantly improved performance. Subsequently, thin MIP films containing FluMa were deposited onto functionalised glass slides and the influence of porogen, drying time, and monomer composition was studied. These MIP-functionalised glass electrodes were mounted into a customised 3D-printed flow cell, where changes in the liquid were either evaluated with a thermal device or using fluorescence bright field microscopy. Thermal analysis demonstrated that multiple MIP layers enhanced sensor specificity, with detection in the environmentally relevant range. The fluorescence bright field microscope investigations validated these results, showing an increase in the fluorescence intensity upon exposure of the MIP-functionalised glass slides to nafcillin solutions. These are promising results for developing a portable sensor device that can be deployed for antibiotics outside of a dedicated laboratory environment, especially if sensor design and fluorophore architecture are optimised.
