Exotoxin A (ExoA) from Pseudomonas aeruginosa is an important virulence factor that belongs to a class of exotoxins that are secreted by pathogenic bacteria which cause human diseases such as cholera, diphtheria, pneumonia and whooping cough. We present the first crystal structures, to our knowledge, of ExoA in complex with elongation factor 2 (eEF2) and intact NAD þ , which indicate a direct role of two active-site loops in ExoA during the catalytic cycle. One loop moves to form a solvent cover for the active site of the enzyme and reaches towards the target residue (diphthamide) in eEF2 forming an important hydrogen bond. The NAD þ substrate adopts a conformation remarkably different from that of the NAD þ analogue, bTAD, observed in previous structures, and fails to trigger any loop movements. Mutational studies of the two loops in the toxin identify several residues important for catalytic activity, in particular Glu 546 and Arg 551, clearly supporting the new complex structures. On the basis of these data, we propose a transition-state model for the toxin-catalysed reaction.
Objectives While bariatric surgery is an effective treatment for individuals living with severe obesity, adhering to dietary requirements, especially protein requirements, can be a challenge. This study aims to examine the suitability of a nutrition-based education tool called “Protein Cards” that is focused on recipes high in protein to support individuals who have completed the surgery. Methods An online survey (23 questions) was developed using an adapted version of the Suitability Assessment of Materials (SAM) instrument along with two additional questions about the participants’ overall impression of the Protein Cards. Sample recipe cards were shown on each page of the survey. Participants were asked to rate the Protein Cards (“Not Suitable”, “Adequate”, or “Superior”) on: Content, Literacy Demand, Graphic Illustrations, Layout & Typography, Learning Stimulation & Motivation, and Cultural Appropriateness. Additionally, participants rated Overall Impression on a scale of 0 to 100. The survey was distributed over email to Canadian bariatric patients (adolescents and adults), dietitians, healthcare workers, and caregivers. Results Twenty participants registered to participate in the survey (Sept 2020-Jan 2021) but only fifteen participants completed the entire survey. Preliminary results revealed “Superior” scores for Content (83%), Learning & Stimulation (81%), Layout & Typography (89%), Literacy Demand (76%), and Cultural Appropriateness (78%). Overall, the recipe cards obtained an average score of 81%, which is considered as a “Superior” evaluation. Participants expressed that they were more likely to use the education tool during the “purée" (82%) and “soft diet” (78%) phases of the post-surgical diet and would prefer if the tool took on the form of a mobile application (85%). Conclusions The Protein Cards are considered a superior education tool that could be helpful when teaching and learning about foods high in protein for the post-operative stages of bariatric surgery. Future work will involve testing the tool in practice with both adolescent and adult patients as a means to increase adherence to post-operative nutrition requirements. Funding Sources University of British Columbia, Faculty of Land and Food Systems.
<p>Ocean surface waves and currents can interact to produce strong seabed shear stress and mobilization of sediments that can significantly impact the seabed stability and benthic habitats on continental shelves. Modelled waves, near-bottom tidal current and circulation current data for a 3-year period were used in a widely applied sediment transport module to simulate the seabed shear stresses and the mobilization of observed sediment grain size on the Scotian Shelf of eastern Canada.</p> <p>The Scotian Shelf is affected by strong waves and tidal currents. These waves, currents and/or their interaction cause maximum mean bed shear velocities of 5 &#8211; 10 cm s<sup>&#8722;1</sup>. Observed sediments on the Scotian Shelf can be mobilized by tidal currents at least once during the modelled 3 year period over 28% of the shelf area while waves can mobilize sediments over 60% of the shelf area suggesting much stronger sediment mobilization by waves. Interaction between waves and currents can produce enhanced combined wave-current shear velocity that is capable to mobilize sediments over 74% of the shelf area. The spatial variation of the relative importance of sediment mobilization frequency by component processes was used to classify the Scotian Shelf into six disturbance types. In comparison with previous studies using depth-averaged tidal currents, the present study based on near-bottom tidal currents has resulted in reduced sediment mobilization frequency by tidal currents, smaller extent of high mobility areas and significant changes of the spatial pattern of disturbance type distribution on the Scotian Shelf. The universal Seabed Disturbance Index and Sediment Mobility Index have also been applied to quantify the seabed exposure to physical processes and sediment mobilization on the Scotian Shelf by accounting for both the magnitude and frequency of these processes. The results of this modelling study are important for environmental assessments and for the spatial planning and management of the Scotian Shelf bioregion.&#160;</p>
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