A Cryptic K48 Ubiquitin Chain Binding Site on UCH37 is Required for its Role in Proteasomal Degradation

Degradation by the 26S proteasome is an intricately regulated process fine-tuned by the precise nature of ubiquitin modifications attached to a protein substrate. By debranching ubiquitin chains composed of K48 linkages, the proteasome-associated ubiquitin C-terminal hydrolase UCHL5/UCH37 serves as a positive regulator of protein degradation. How UCH37 achieves specificity for K48 chains is unclear. Here, we use a combination of hydrogen-deuterium mass spectrometry, chemical crosslinking, small-angle X-ray scattering, NMR, molecular docking, and targeted mutagenesis to uncover a cryptic K48 ubiquitin chain specific binding site on the opposite face of UCH37 relative to the canonical S1 ubiquitin-binding site. Biochemical assays demonstrate the K48 chain-specific binding site is required for chain debranching and proteasome-mediated degradation of proteins modified with branched chains. Using quantitative proteomics, translation shutoff experiments, and linkage-specific affinity tools, we then identify specific proteins whose degradation depends on the debranching activity of UCH37. Our findings suggest that UCH37 and potentially other DUBs could use more than one S1 site to perform different biochemical functions.

Heavy Metals Adsorption on Cellulosic Materials from Agricultural Waste

Adsorption technique has been known to be a very effective method for treatment of heavy metals polluted wastewater, with the advantages of specific affinity, simple design and being user-friendly. However, the high cost of activated carbon commonly used as the adsorbent makes it necessary to explore the use of cheap cellulosic adsorbents. In this study, the adsorptive property of sugarcane bagasse (SB) and orange mesocarp (OM) was investigated. The cellulosic adsorbents were used for the sorption of lead and zinc ions from aqueous solutions. The effects of varying adsorbent dose, varying contact time and initial metal ion concentration on adsorption process of the metals were studied. The results show that both adsorbents (though waste materials) are viable for removal of metals from wastewater. Moreover, SB had higher sorption capacity for zinc (12.95 for SB and 12.68 for OM) while OM had higher sorption capacity for lead (9.90 for OM and 9.48 for SB) at optimum dosage. The isothermal studies shows that for lead adsorption, experimental data best fitted the Langmuir isotherm for both adsorbents (R2 of 0.9574 for OM and 0.98 for SB) while the data for zinc adsorption best fitted into Freundlich isotherm with SB (R2 of 0.9565)and Langmuir isotherm for OM(R2 of 0.814).

Heavy Metals Adsorption on Cellulosic Materials from Agricultural Waste

Adsorption technique has been known to be a very effective method for treatment of heavy metals polluted wastewater, with the advantages of specific affinity, simple design and being user-friendly. However, the high cost of activated carbon commonly used as the adsorbent makes it necessary to explore the use of cheap cellulosic adsorbents. In this study, the adsorptive property of sugarcane bagasse (SB) and orange mesocarp (OM) was investigated. The cellulosic adsorbents were used for the sorption of lead and zinc ions from aqueous solutions. The effects of varying adsorbent dose, varying contact time and initial metal ion concentration on adsorption process of the metals were studied. The results show that both adsorbents (though waste materials) are viable for removal of metals from wastewater. Moreover, SB had higher sorption capacity for zinc (12.95 for SB and 12.68 for OM) while OM had higher sorption capacity for lead (9.90 for OM and 9.48 for SB) at optimum dosage. The isothermal studies shows that for lead adsorption, experimental data best fitted the Langmuir isotherm for both adsorbents (R2 of 0.9574 for OM and 0.98 for SB) while the data for zinc adsorption best fitted into Freundlich isotherm with SB (R2 of 0.9565) and Langmuir isotherm for OM (R2 of 0.814).

Human Recombinant Leptin Shows Dose and Time-Dependent Release of Nitric Oxide from Endothelial Nitric Oxide Synthase in Endothelium While on Angiogenesis

Nitric Oxide (NO) modulates various assortments of the angiogenic process. The endogenous hormone leptin is able to induce different physiological process such as angiogenesis at low concentration because of its high receptor specific affinity. Various studies speculated leptin’s ability to induce endothelium‐dependent vascular relaxation by stimulating NO through different signaling pathways. So far, no studies have reported the dose and time dependent potential of human recombinant leptin on NO release. Hence, an attempt has been made to understand the optimal concentration and time of incubation of human recombinant leptin for the enzymatic release of NO from endothelial Nitric Oxide Synthase (eNOS). Leptin induced changes in the localization and phosphorylation pattern of eNOS in cultured endothelium under various concentrations and time of incubation is studied. The 5 Nanomolar concentration of human recombinant leptin within 6 minutes of incubation could induce significant levels of NO from the activated eNOS in cultured endothelium through plasma membrane localization and phosphorylation of eNOS. Our findings suggest that human recombinant leptin can modulate NO-dependent new therapeutic avenue for angiogenesis-related disorders such as wound healing if used within the active concentration and time of incubation.

Aquatic Plants as Bioremediators in Pollution Abatement of Heavy Metals

Over use of chemical inputs and exploitation of natural resources have degraded our ecosystem to a large extent. Our water bodies are drastically affected, especially due to the impact of heavy metal loading. The biomagnification that results from these difficult to degrade metals is naturally affecting the human health. The physical and chemical methods commonly employed for water purification are not only highly expensive but also further aggravate the pollution problem. Hence, all efforts must be taken to exploit the emerging green technology approach in pollution remediation. Several aquatic plants have specific affinity towards heavy metals and they flourish well in this contaminated environment. The common mechanisms of phytoremediation and varied type of aquatic plants with high remediation potential are reviewed in this chapter.

Non-specific adhesive forces between filaments and membraneless organelles

Membraneless organelles are liquid-like domains that form inside living cells by phase-separation. While standard physical models of their formation assume their surroundings to be a simple liquid, the cytoplasm is an active viscoelastic environment. To investigate potential coupling of phase separation with the cytoskeleton, we quantify structural correlations of stress granules and microtubules in a human-derived epithelial cell line. We find that microtubule networks are significantly perturbed in the vicinity of stress granules, and that large stress granules conform to the local pore-structure of the microtubule network. When microtubules are depolymerized by nocodazole, tubulin enrichment is localized near the surface of stress granules. We interpret these data using a thermodynamic model of partitioning of particles to the surface and bulk of droplets. This analysis shows that proteins generically have a non-specific affinity for droplet interfaces, which becomes most apparent when they weakly partition to the bulk of droplets and have a large molecular weight. In this framework, our data is consistent with a weak (lower than kbT) affinity of tubulin sub-units for stress granule interfaces. As microtubules polymerize their affinity for interfaces increases, providing sufficient adhesion to deform droplets and/or the network. We validate this basic physical phenomena in vitro through the interaction of a simple protein-RNA condensate with tubulin and microtubules.