Background: Rhomboid proteases are ubiquitous, and their role in Archaea has not been explored. Results: We generated a rhomboid deletion mutant that displayed a glycosylation defect. Conclusion: Deletion of a rhomboid protease gene altered S-layer glycoprotein N-glycosylation. Significance: This work provides structural characterization of a novel oligosaccharide bound to H. volcanii S-layer glycoprotein and relates a rhomboid protease with the protein glycosylation process.
Cruzipain (Cz), the major cysteine proteinase of Trypanosoma cruzi, is a glycoprotein that contains sulfated high‐mannose‐type oligosaccharides. We have previously determined that these sulfate groups are targets of specific immune responses. In order to evaluate the structural requirements for antibody recognition of Cz, a systematic structure–activity study of the chemical characteristics needed for antibody binding to the Cz sulfated epitope was performed by immunoassays. With this aim, different synthesized molecules were coupled to the proteins BSA and aprotinin and confronted with (a) mouse sera specific for Cz and its carboxy‐terminal (C‐T) domain, (b) antibodies raised in rabbits immunized with Cz and its C‐terminal domain and (c) IgGs purified from human Chagas disease sera. Our results indicate that a glucosamine containing an esterifying sulfate group in position O‐6 and an N‐acetyl group was the preferred epitope for the immune recognition of sera specific for Cz and its C‐T domain. Although to a minor extent, other anionic compounds bearing sulfate groups in different positions and number as well as different anionic charged groups including carboxylated or phosphorylated monosaccharides, disaccharides and oligosaccharides were recognized. In conclusion, we found that synthetic anionic sugar conjugates containing N‐acetyl d‐glucosamine‐6‐sulfate sodium salt (GlcNAc6S) competitively inhibit the binding of affinity purified rabbit anti‐C‐T IgG to the C‐T extension of Cz. Extending these findings to the context of natural infection, immune assays performed with Chagas disease serum confirmed that the structure of synthetic GlcNAc6S mimics the N‐glycan‐linked sulfated epitope displayed in the C‐T domain of Cz.
In the current study the ability of copper complex to exert multiple biological activities is combined with the pharmacological action of sertraline (SerHCl, antidepressant drug). The hydrated and anhydrous forms of the tetrachlorocuprate(II) salts, namely (SerH)[CuCl]·½HO and (SerH)[CuCl], were synthesized and characterized by physicochemical methods. The crystal structures were determined by X-ray diffraction methods. The hydrate complex crystallizes in the monoclinic P2 space group with a=8.0807(2) Å, b=36.2781(8) Å, c=12.6576(3) Å, β=95.665(2)°, and Z=4 molecules per unit cell and the un-hydrate in P2 with a=13.8727(6) Å, b=7.5090(3) Å, c=18.618(1) Å, β=104.563(6)°, and Z=2. It has been suggested that Cu(II) ions might be critical in the development of mood disorders, showed potent biocidal activity, and also acted as analgesic adjuvant. To improve sertraline efficiency, the antidepressant and analgesic activities of the complex have been assessed in rats denoting a marked synergistic effect. Antithyroid and antimicrobial activities were also evaluated. Because depressive disorders and hyperthyroidism diseases led to an oxidative stress state, antioxidant capability has also been tested. The complex behaved as a good superoxide radical scavenger (IC=6.3×10M). The ability of the complex to act as bromoperoxidase mimic was assessed. A pseudo-first order constant of k=0.157±0.007min has been determined. The complex evidences promising biological-pharmacological activities and the albumin binding studies showed a K of 2.90×10M showing an improvement in the uptake of sertraline by albumin at 8h incubation (time required for effective interaction of sertraline with the protein).
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