Obesity is a major threat to global health and metabolically associated with glycerol homeostasis. Here we demonstrate that in human adipocytes, the decreased pH observed during lipolysis (fat burning) correlates with increased glycerol release and stimulation of aquaglyceroporin AQP10. The crystal structure of human AQP10 determined at 2.3 Å resolution unveils the molecular basis for pH modulation—an exceptionally wide selectivity (ar/R) filter and a unique cytoplasmic gate. Structural and functional (in vitro and in vivo) analyses disclose a glycerol-specific pH-dependence and pinpoint pore-lining His80 as the pH-sensor. Molecular dynamics simulations indicate how gate opening is achieved. These findings unravel a unique type of aquaporin regulation important for controlling body fat mass. Thus, targeting the cytoplasmic gate to induce constitutive glycerol secretion may offer an attractive option for treating obesity and related complications.

21Phosphorous has long been the target of much research, but in recent years the focus has 22shifted from being limited only to reducing its detrimental environmental impact, to also looking 23 at how it is linked to the global food security. Therefore, the interest in finding novel techniques 24 for phosphorous recovery, as well as improving existing techniques, has increased. In this study 25we apply a hybrid simulation approach of molecular dynamics and quantum mechanics to 26 investigate the binding modes of phosphate anions by a small intrinsically disordered peptide. 27Our results confirm that the conformational ensemble of the peptide is significantly changed, or 28 stabilized, by the binding of phosphate anions and that binding does not take place purely as a 29 result of a stable P-loop binding nest, but rather that multiple binding modes may be involved. 30Such small synthetic peptides capable of binding phosphate could be the starting point of new 31 novel technological approaches towards phosphorus recovery, and they represent an excellent 32 model system for investigating the nature and dynamics of functional de novo designed 33 intrinsically disordered proteins. 34 2 Introduction 35 Phosphorous (P) is an essential element in terms of sustaining the world's current and 36 future food supply, for which there is no substitute. [1][2][3] Given that the current P supply is based on 37 the gradual depletion of limited fossil reserves, an increasing demand for P necessitates a change 38 towards more sustainable practices where P is recovered from the large waste streams. The 39 lifetime of remaining high quality phosphate rocks is still being debated, estimates varying from a 40 few decades to a few hundred years. 3,4 There is however a general consensus that P is becoming 41 more and more difficult to access, costs are increasing, more waste is being produced, and the 42 3 global demand is expected to increase. 4,5 Meanwhile, only a fraction of the mined P makes it into 43 the intended plants and animals which humans consume, while most is lost along the way causing 44 serious environmental problems e.g. by eutrophication of lakes, reservoirs, estuaries, and parts of 45 the ocean. 2,4,6,7 46The topic of P has been a point of interest for waste-water treatment engineers for 47 decades. 8 The main attention has however so far been focused almost exclusively on reducing 48 eutrophication, so while many of the now common techniques for P treatment, e.g. chemical 49 precipitation 8 and enhanced biological phosphorus removal 9 (EBPR), are highly efficient for the 50 job they were designed for, they are not necessarily effective in terms of recovering P from its 51 large waste flows, which have different characteristics from the commonly treated domestic 52 wastewater flows and are not always easily intercepted (e.g. erosion and runoff 2 ). One of the 53 current main technologies, optimized for P removal but also applicable to recovery to some 54 extent, is EBPR, where polyphosphate accumulating ...

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Forward osmosis (FO) membranes have gained interest in several disciplines for the rejection and concentration of various molecules. One application area for FO membranes that is becoming increasingly popular is the use of the membranes to concentrate or dilute high value compound solutions such as pharmaceuticals. It is crucial in such settings to control the transport over the membrane to avoid losses of valuable compounds, but little is known about the rejection and transport mechanisms of larger biomolecules with often flexible conformations. In this study, transport of two chemically similar peptides with molecular weight (Mw) of 375 and 692 Da across a thin film composite Aquaporin Inside™ Membrane (AIM) FO membrane was investigated. Despite the relative large size, both peptides were able to permeate the dense active layer of the AIM membrane and the transport mechanism was determined to be diffusion-based. Interestingly, the membrane permeability increased 3.65 times for the 692 Da peptide (1.39 × 10−12 m2·s−1) compared to the 375 Da peptide (0.38 × 10−12 m2·s−1). This increase thus occurs for an 85% increase in Mw but only for a 34% increase in peptide radius of gyration (Rg) as determined from molecular dynamics (MD) simulations. This suggests that Rg is a strong influencing factor for membrane permeability. Thus, an increased Rg reflects the larger peptide chains ability to sample a larger conformational space when interacting with the nanostructured active layer increasing the likelihood for permeation.

of isolated b-hairpin peptides have focused on stabilizing three elements of b-hairpin structure: individual b-strands, cross-strand interactions, and the reverse turn. Though these strategies have produced a variety of stable, wellfolded b-hairpins, the stabilizing moieties often occupy potential functional sites that might interfere with the design of b-hairpin PPI inhibitors. To overcome this limitation, we evaluated the hydrogen bond surrogate (HBS) approach as a sequence-independent strategy to generate stable b-hairpin PPI inhibitors. The HBS approach replaces a structural main-chain hydrogen bond with an isosteric covalent bond and has been particularly successful for stabilization of peptides in the a-helical conformation. We have recently shown that HBS mimicry of the N-to-C-terminal hydrogen bond of a model b-hairpin leads to a thermally and proteolytically stable b-hairpin.Here we show that the HBS approach is generalizable to other b-hairpins and apply it to the design of b-hairpin PPI inhibitors. Specifically, we evaluated a critical b-hairpin fragment in the NS1 monobody, which inhibits Ras dimerization and signaling. We show that NS1-derived HBS b-hairpins bind to Ras in vitro and affect cell proliferation in Ras-dependent cell lines. These NS1 HBS b-hairpins will be useful as research tools to study Ras signaling. We envision that the HBS approach will be useful in the generation of additional b-hairpin PPI inhibitors and will provide a ''stepping stone'' for the creation of stable, sequence-independent b-sheet PPI inhibitors.