a b s t r a c tZinc-a2-glycoprotein (ZAG) is an adipokine with an MHC class I-like protein fold. Even though zinc causes ZAG to precipitate from plasma during protein purification, no zinc binding has been identified to date. Using mass spectrometry, we demonstrated that ZAG contains one strongly bound zinc ion, predicted to lie close to the a1 and a2 helical groove. UV, CD and fluorescence spectroscopies detected weak zinc binding to holo-ZAG, which can bind up to 15 zinc ions. Zinc binding to 11-(dansylamino) undecanoic acid was enhanced by holo-ZAG. Zinc binding may be important for ZAG binding to fatty acids and the b-adrenergic receptor.
Zinc α2 glycoprotein (ZAG) is an adipokine with a class I MHC protein fold and is associated with obesity and diabetes. Although its intrinsic ligand remains unknown, ZAG binds the dansylated C11 fatty acid 11-(dansylamino)undecanoic acid (DAUDA) in the groove between the α1 and α2 domains. The surface of ZAG has approximately 15 weak zinc-binding sites deemed responsible for precipitation from human plasma. In the present study the functional significance of these metal sites was investigated. Analytical ultracentrifugation (AUC) and CD showed that zinc, but not other divalent metals, causes ZAG to oligomerize in solution. Thus ZAG dimers and trimers were observed in the presence of 1 and 2 mM zinc. Molecular modelling of X-ray scattering curves and sedimentation coefficients indicated a progressive stacking of ZAG monomers, suggesting that the ZAG groove may be occluded in these. Using fluorescence-detected sedimentation velocity, these ZAG-zinc oligomers were again observed in the presence of the fluorescent boron dipyrromethene fatty acid C16-BODIPY (4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-hexadecanoic acid). Fluorescence spectroscopy confirmed that ZAG binds C16-BODIPY. ZAG binding to C16-BODIPY, but not to DAUDA, was reduced by increased zinc concentrations. We conclude that the lipid-binding groove in ZAG contains at least two distinct fatty acid-binding sites for DAUDA and C16-BODIPY, similar to the multiple lipid binding seen in the structurally related immune protein CD1c. In addition, because high concentrations of zinc occur in the pancreas, the perturbation of these multiple lipid-binding sites by zinc may be significant in Type 2 diabetes where dysregulation of ZAG and zinc homoeostasis occurs.
Smart grid technology has given users the ability to regulate their home energy in a much more effective manner. In such scenarios, Home Energy Management (HEM) potentially becomes an arduous task, as it necessitates the optimal scheduling of smart appliances in order to reduce energy usage. In this research, a hybrid Harris Hawk Optimization-Sine Cosine Algorithm (hHHO-SCA) has been proposed to develop a meta-heuristic-based HEM system. The hybridization of HHO with SCA has been done to enhance the exploration and exploitation stages of HHO, hence improving its global search phase and effectively optimizing the energy usages. In addition to this, several knapsacks are utilized to guarantee that load demand for power users does not surpass a certain level during the peak hours. In terms of electricity prices and Peak to Average Ratio (PAR) reduction, the hybridization is demonstrated to be beneficial in achieving the objectives. Simulations are performed for a multi-family housing complex with a range of smart equipment. The results achieved with the proposed approach suggest that hHHO-SCA has been comparatively efficient in terms of cost reduction, and PAR, when compared to the other optimization techniques. Practical Application. This home energy management system can be applied to optimally schedule all the smart appliances in a building to minimize electricity consumption and provide the consumer with potential savings in electricity costs.
Iron is indispensable for the eukaryotic cell but excess of iron is toxic. Disruptions in iron metabolism leads to numerous human diseases, hence the study of iron regulation and metabolism is of high importance. Saccharomyces cerevisiae is used as a model system in our lab to study iron trafficking and homeostasis pathways to better understand iron regulation at the cellular and molecular level. In yeast, two paralogous transcriptional activators, Aft1 and Aft2, play a central role in iron regulation by activating the transcription of target genes in response to iron deprivation. Monothiol glutaredoxins Grx3 and Grx4 that utilize glutathione to bind [2Fe‐2S] clusters interact specifically with Aft1 and Aft2, transferring an Fe‐S cluster to Aft1/2 that inhibits its DNA binding activity. Aft1 is considered the primary regulator of iron homeostasis because aft1Δ mutants exhibit a stronger iron deficiency phenotype than aft2Δ mutants. Aft1 and Aft2 share 39% sequence homology in their N‐terminal DNA binding domains. The only available structure is of a truncated version of Aft2 that contains this homologous portion and includes the domains responsible for DNA binding and iron sensing. Aft1/2 have been shown to be very unstable and difficult to overexpress and purify in Escherichia coli. Hence we optimized the growth conditions to overexpress Aft1 in its native organism, Saccharomyces cerevisiae, and further try to purify Aft1 from the same. Further studies will be carried out in order to investigate the in‐vitro interaction between full length Aft1/2 and Grx3/4‐Fra2 to better understand the mechanism of Aft1/2 inhibition at the molecular level.Support or Funding InformationSupported by Dr. Caryn E. Outten's Research FundingThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.
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