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Angelman syndrome (AS) is a rare neurodevelopmental disorder characterized by speech impairment, intellectual disability, ataxia, and epilepsy. AS is caused by mutations in the maternal copy of UBE3A located on chromosome 15q11-13. UBE3A codes for E6AP (E6 Associated Protein), a prominent member of the HECT (Homologous to E6AP C-Terminus) E3 ubiquitin ligase family. E6AP catalyzes the posttranslational attachment of ubiquitin via its HECT domain onto various intracellular target proteins to regulate DNA repair and cell cycle progression. The HECT domain consists of an N-lobe, required for E2~ubiquitin recruitment, while the C-lobe contains the conserved catalytic cysteine required for ubiquitin transfer. Previous genetic studies of AS patients have identified point mutations in UBE3A that result in amino acid substitutions or premature termination during translation. An AS transversion mutation (codon change from ATA to AAA) within the region of the gene that codes for the catalytic HECT domain of E6AP has been annotated (I827K), but the molecular basis for this loss of function substitution remained elusive. Here, we demonstrate that the I827K substitution destabilizes the 3D fold causing protein aggregation of the C-terminal lobe of E6AP using a combination of spectropolarimetry and nuclear magnetic resonance (NMR) spectroscopy. Our fluorescent ubiquitin activity assays with E6AP-I827K show decreased ubiquitin thiolester formation and ubiquitin discharge. Using 3D models in combination with our biochemical and biophysical results, we rationalize why the I827K disrupts E6AP-dependent ubiquitylation. This work provides new insight into the E6AP mechanism and how its malfunction can be linked to the AS phenotype.

There are 28 unique human members of the homologous to E6AP C-terminus (HECT) E3 ubiquitin ligase family. Each member of the HECT E3 ubiquitin ligases contains a conserved bilobal HECT domain of approximately 350 residues found near their C-termini that is responsible for their respective ubiquitylation activities. Recent studies have begun to elucidate specific roles that each HECT E3 ubiquitin ligase has in various cancers, age-induced neurodegeneration, and neurological disorders. New structural models have been recently released for some of the HECT E3 ubiquitin ligases, but many HECT domain structures have yet to be examined due to chronic insolubility and/or protein folding issues. Building on these recently published structural studies coupled with our in-house experiments discussed in the present study, we suggest that the addition of ∼50 conserved residues preceding the N-terminal to the current UniProt defined boundaries of the HECT domain are required for isolating soluble, stable, and active HECT domains. We show using in silico bioinformatic analyses coupled with secondary structural prediction software that this predicted N-terminal α-helix found in all 28 human HECT E3 ubiquitin ligases forms an obligate amphipathic α-helix that binds to a hydrophobic pocket found within the HECT N-terminal lobe. The present study brings forth the proposal to redefine the residue boundaries of the HECT domain to include this N-terminal extension that will likely be critical for future biochemical, structural, and therapeutic studies on the HECT E3 ubiquitin ligase family.

Mutations in Parkin are one of the predominant hereditary factors found in patients suffering from autosomal recessive juvenile Parkinsonism. Parkin is a member of the E3 ubiquitin ligase family that is defined by a tripartite RING1-in-between-ring (IBR)-RING2 motif. In Parkin, the IBR domain has been shown to augment binding of the E2 proteins UbcH7 and UbcH8, and the subsequent ubiquitination of the proteins synphilin-1, Sept5, and SIM2. To facilitate our understanding of Parkin function, the solution structure of the Parkin IBR domain was solved by using NMR spectroscopy. Folding of the IBR domain (residues M327-S378) was found to be zinc dependent, and the structure reveals the domain forms a unique pair scissor-like and GAG knuckle-like zinc-binding sites, different from other zinc-binding motifs such as the RING, LIM, PHD, or B-box motifs. The N terminus of the IBR domain, residues E307-E322, is unstructured. The disease causing mutation T351P causes global unfolding, whereas the mutation R334C causes some structural rearrangement of the domain. In contrast, the protein containing the mutation G328E appears to be properly folded. The structure of the Parkin IBR domain, in combination with mutational data, allows a model to be proposed where the IBR domain facilitates a close arrangement of the adjacent RING1 and RING2 domains to facilitate protein interactions and subsequent ubiquitination.

Genetic recombination in bacteriophage λ relies on DNA end processing by Exo to expose 3′-tailed strands for annealing and exchange by β protein. Phage λ encodes an additional recombinase, Orf, which participates in the early stages of recombination by supplying a function equivalent to the Escherichia coli RecFOR complex. These host enzymes assist loading of the RecA strand exchange protein onto ssDNA coated with ssDNA-binding protein. In this study, we purified the Orf protein, analyzed its biochemical properties, and determined its crystal structure at 2.5 Å. The homodimeric Orf protein is arranged as a toroid with a shallow U-shaped cleft, lined with basic residues, running perpendicular to the central cavity. Orf binds DNA, favoring single-stranded over duplex and with no obvious preference for gapped, 3′-tailed, or 5′-tailed substrates. An interaction between Orf and ssDNA-binding protein was indicated by far Western analysis. The functional similarities between Orf and RecFOR are discussed in relation to the early steps of recombinational exchange and the interplay between phage and bacterial recombinases.

Casual games are everywhere. People play them throughout life to pass the time, to engage in social interactions, and to learn. However, their simplicity and use in distraction-heavy environments can attenuate their potential for learning. This experimental study explored the effects playing an online, casual game has on awareness of human biological systems. Two hundred and forty-two children were given pretests at a Museum and posttests at home after playing either a treatment or control game. Also, 41 children were interviewed to explore deeper meanings behind the test results. Results show modest improvement in scientific attitudes, ability to identify human biological systems and in the children's ability to describe how those systems work together in real-world scenarios. Interviews reveal that children drew upon their prior school learning as they played the game. Also, on the surface they perceived the game as mainly entertainment but were easily able to discern learning outcomes when prompted. Implications for the design of casual games and how they can be used to enhance transfer of knowledge from the classroom to everyday life are discussed.

Polyamines are essential in all branches of life. Spermidine synthase (putrescine aminopropyltransferase, PAPT) catalyzes the biosynthesis of spermidine, a ubiquitous polyamine. The crystal structure of the PAPT from Thermotoga maritima (TmPAPT) has been solved to 1.5 Å resolution in the presence and absence of AdoDATO (S-adenosyl-1,8-diamino-3-thiooctane), a compound containing both substrate and product moieties. This, the first structure of an aminopropyltransferase, reveals deep cavities for binding substrate and cofactor, and a loop that envelops the active site. The AdoDATO binding site is lined with residues conserved in PAPT enzymes from bacteria to humans, suggesting a universal catalytic mechanism. Other conserved residues act sterically to provide a structural basis for polyamine specificity. The enzyme is tetrameric; each monomer consists of a C-terminal domain with a Rossmann-like fold and an N-terminal β-stranded domain. The tetramer is assembled using a novel barrel-type oligomerization motif.

[...]we asked practitioners working in countries around the globe to add to and broaden our global view of career development. [...]we focused on three major areas: * the impact of technology on the workplace * working in the fourth industrial revolution * how career practitioners will work in the future I have been fascinated with learning about factories of the future, not just in North America but in other countries, such as China, for an awfully long time. [...]several sources point out that any definition of advanced manufacturing will need to change with the changing times, and that the definition will vary for different companies and different industries\" (\"Advanced Manufacturing,\" 2020). To help us and our clients continue to do great work in changing times, the following practitioners shared their expertise: * Dr.William Huffaker and Anitah Gombos identify how we will need to reskill the industry leaders of tomorrow. * Dr. Sarah Eaton, a leader in her field, shares her knowledge on academic integrity and counterfeit credentials. * Kelley Steven Waiss and Edie Goldberg, authors of The Inside Gig: How Sharing Untapped Talent Across Boundaries Unleashes Organizational Capacity, share their knowledge on how the gig economy is being used inside organizations, and Kelley Steven Waiss also shares how HR leaders will need to act as supply chain talent managers. * The Futureproof Workplace authors Morag Barrett and Dr. Linda Sharkey, along with Lou Carter, provide insights into how employers and employees will need to adapt to the post pandemic and changing workplace. * Social media expert Dr. Nancy Richmond shares her knowledge on how social media can be used effectively within organizations. * Ann Nakaska adds an article on what our clients can expect in the office of the future. * Kate Brooks explores job search in the fourth industrial revolution, based on Dick Bolles work, What Color is Your Parachute?. * Jenn Long Leard shares her knowledge on how we can reinvent career services for the fourth industrial revolution. * Dr. Rich Feller wraps up the journal with wisdom on how we can move forward through the fourth industrial revolution with new skills while continuing to honour those who came before us, with a tribute to the legacy of Dick Bolles.