Sequence analysis and expression of a cDNA clone encoding tropomysin in Sinonovacula constricta

Crystallographic characterization of ferritin from Sinonovacula constricta

Ferritins are ubiquitous iron-binding proteins that are mainly related to iron storage, detoxification and innate immunity. Here, we present the crystal structure of a marine invertebrate ferritin from Sinonovacula constricta at a resolution of 1.98 Å. The S. constricta ferritin (ScFer) possessed some structural similarities with vertebrate ferritins, and they shared a well-conserved architecture composed of five α-helical bundles that assembled into a cage-like structure with 24-subunits. The structure of ScFer also showed iron binding sites in the 3-fold channel, ferroxidase center, and putative nucleation sites. Further, electrostatic potential calculations suggested that the electrostatic gradient of the 3-fold channel could provide a guidance mechanism for iron entering the ferritin cavity.

Seafood allergy: A comprehensive review of fish and shellfish allergens

Seafood refers to several distinct groups of edible aquatic animals including fish, crustacean, and mollusc. The two invertebrate groups of crustacean and mollusc are, for culinary reasons, often combined as shellfish but belong to two very different phyla. The evolutionary and taxonomic diversity of the various consumed seafood species poses a challenge in the identification and characterisation of the major and minor allergens critical for reliable diagnostics and therapeutic treatments. Many allergenic proteins are very different between these groups; however, some pan-allergens, including parvalbumin, tropomyosin and arginine kinase, seem to induce immunological and clinical cross-reactivity. This extensive review details the advances in the bio-molecular characterisation of 20 allergenic proteins within the three distinct seafood groups; fish, crustacean and molluscs. Furthermore, the structural and biochemical properties of the major allergens are described to highlight the immunological and subsequent clinical cross-reactivities. A comprehensive list of purified and recombinant allergens is provided, and the applications of component-resolved diagnostics and current therapeutic developments are discussed.

Characterization of Sarcoptes scabiei Tropomyosin and Paramyosin: Immunoreactive Allergens in Scabies

Scabies is a human skin disease due to the burrowing ectoparasite Sarcoptes scabiei var. hominis resulting in intense itching and inflammation and manifesting as a skin allergy. Because of insufficient mite material and lack of in vitro propagation system for antigen preparation, scabies is a challenging disease to develop serological diagnostics. For allergen characterization, full-length S. scabiei tropomyosin (Sar s 10) was cloned, expressed in pET-15b, and assessed for reactivity with IgE antibodies from human sera. IgE binding was observed to Sar s 10 with sera collected from subjects with ordinary scabies, house dust mite (HDM)-positive and naive subjects and a diagnostic sensitivity of < 30% was observed. S. scabiei paramyosin (Sar s 11) was cloned, and expressed in pET-28a in three overlapping fragments designated Sspara1, Sspara2, and Sspara3. IgE and IgG binding was observed to Sspara2 and Sspara3 antigens with sera collected from ordinary scabies, and HDM-positive subjects, but no binding was observed with sera collected from naive subjects. Sspara2 displayed excellent diagnostic potential with 98% sensitivity and 90% specificity observed for IgE binding and 70% sensitivity for IgG. In contrast, the diagnostic sensitivity of Sspara3 was 84% for IgE binding and 40% for IgG binding. In combination, Sspara2 and Sspara3 provided an IgE sensitivity of 94%. This study shows that IgE binding to Sspara2 and Sspara3 is a highly sensitive method for diagnosis of scabies infestation in clinical practice. The developed enzyme-linked immunosorbent assay helps direct future development of a specific diagnostic tool for scabies.

Structural Characterization and Immunostimulatory Activity of a Homogeneous Polysaccharide from Sinonovacula constricta

Sinonovacula constricta has been widely used as a health food and medicine in China, Japan, and Korea. In the present study, a water-soluble polysaccharide fraction (SCP-1) was prepared from S. constricta by enzyme-assisted extraction and purification of chromatography with DEAE-52 cellulose anion-exchange column and Sephadex G-100 size exclusion column. On the basis of the analytical results of high-performance liquid chromatography, Fourier transform-infrared spectroscopy, methylation analysis, and NMR spectroscopy, SCP-1 was found to have an average molecular weight of 15.63 kDa and a linear backbone of (1→4)-linked α-D-Glcp residue with one branch, α-D-Glcp, attached to the main chain by a (1→6) glycosidic bond at every five α-D-Glcp units. Furthermore, it was found that SCP-1 could significantly increase the viability of macrophages, enhance the capability of macrophage phagocytosis, increase the activity of acid phosphatase, and promote the production of nitric oxide, mouse tumor necrosis factor (TNF)-α, mouse interferon (IFN)-γ, and mouse interleukin (IL)-1β. The results suggest that SCP-1 possesses potent immunomodulating effect and may be explored as a potential biological response modifier.

The group 10 allergen of Dermatophagoides farinae (Acari: Pyroglyphidae): cDNA cloning, sequence analysis, and expression in Escherichia coli BL21

Dermatophagoides farinae Hughes, American house dust mite, is highly allergenic, producing symptoms in people worldwide. Identifying and cloning the allergens in this species may enable better diagnostic and therapeutic approaches. Here, we cloned, sequenced, and expressed the full-length cDNA encoding D. farinae group 10 allergen (Der f 10) isolated from dust mites in China. Bioinformatic analysis indicated that the 888 bp sequence encoded a cytoskeleton protein 295 amino acids long, with a molecular weight of approximately equal 34 kDa. Sequence alignment with the group 10 allergens of Pyroglyphidae, Acaridae, and Glycyphagidae families revealed that the group 10 allergen from D. farinae is 95% similar to D. pteronyssinus Trouessart and Psoroptes ovis (Hering). These findings lay the groundwork for future studies, including large-scale production of recombinant Der f 10 allergen for diagnostic and therapeutic agents.

Molecular cloning, expression, sequence analyses of dust mite allergen Der f 6 and its IgE-binding reactivity with mite allergic asthma patients in southeast China

We report the cloning and molecular characterization of a full-length cDNA encoding house dust mite allergen, Der f 6 from D. farinae isolated in China. The full-length Der f 6 cDNA was obtained with 840 nucleotides long. Nucleotide sequencing analyses showed a total of 36 mutations in five Der f 6 cDNA clones, corresponding to 23 incompatible amino acid residues. Recombinant Der f 6 (rDer f 6) protein was successfully expressed in and purified from E. coli BL21. Among 20 asthmatic patients, 45% was positive to rDer f 6 by ELISA. Bioinformatics analyses revealed that the mature Der f 6 was a hydrophobic and extracellular protein with chymotrypsin-like serine protease activity, its secondary structure was composed of alpha helix (7.69%), extended strand (34.62%), random coils (57.69%), and the similarity of Der f 6 to Blo t 6, Sui m 6, Der f 3 and Der f 9 was 64, 65, 35, and 38%, respectively.

Liquid chromatography and mass spectrometry in food allergen detection

Food allergy is an important issue in the field of food safety because of the hazards for affected persons and the hygiene requirements and legal regulations imposed on the food industry. Consumer protection and law enforcement require suitable analytical techniques for the detection of allergens in foods. Immunological methods are currently preferred; however, confirmatory alternatives are needed. The determination of allergenic proteins by liquid chromatography and mass spectrometry has greatly advanced in recent years, and gel-free allergenomics is becoming a routinely used approach for the identification and quantitation of food allergens. The present review provides a brief overview of the principles of proteomic procedures, various chromatographic set ups, and mass spectrometry instrumentation used in allergenomics. A compendium of published liquid chromatography methods, proteomic analyses, typical marker peptides, and quantitative assays for 14 main allergy-causing foods is also included.