Three crystal structures of a lipoprotein (Bmlp7) of unknown function, a member of the 30 kDa lipoprotein family from mulberry silkworm (Bombyx mori L.) haemolymph, have been determined. The 1.33 Å resolution structure is an excellent example of how a precise crystallographic study can contribute to protein identification. The correct sequence of this haemolymph-isolated protein was assigned thanks to superb-quality electron-density maps. Two unexpected cadmium cations were found in this crystal structure [Bmlp7-I(Cd)] and their presence may be connected to a detoxification mechanism in this insect. For a comparison of the metal-binding sites, the crystal structure of a platinum complex (Bmlp7-Pt) was also solved at 1.94 Å resolution. The third (2.50 Å resolution) structure, of the native protein harvested in a different season (Bmlp7-II), corresponds to a different polymorph with an altered pattern of intermolecular interactions and with a total absence of cadmium ions and highlights the possible involvement of Bmlp7 in the response to environmental pollution. The N-terminal domain of Bmlp7 has a fold resembling a clockwise spiral created by six helices and can be classified as a VHS domain. The C-terminal domain is folded as a β-trefoil. The biological function of Bmlp7 is unknown, but its structural homology to sugar-binding proteins suggests that, in analogy to other 30 kDa haemolymph lipoproteins, it could play a role as an anti-apoptotic factor or function in the immune response of the insect to fungal infections.
Juvenile hormone-binding protein (JHBP) and the low-molecular-mass lipoprotein PBMHP-12 belong to a group of 30 kDa proteins that comprise the major protein component of the haemolymph specific to the fifth-instar larvae stage of the mulberry silkworm Bombyx mori L. Proteins from this group are often essential for the development of the insect. In a project aimed at crystallographic characterization of B. mori JHBP (BmJHBP), it was copurified together with PBMHP-12. Eventually, the two proteins were isolated and crystallized separately. The BmJHBP crystals were orthorhombic (space group C222 1 ) and the PBMHP-12 crystals were triclinic. The crystals diffracted X-rays to 2.9 Å (BmJHBP) and 1.3 Å (PBMHP-12) resolution.
Long-term fungal infections that are difficult to treat require new substances for their prevention, treatment, or as adjuvants during antibiotic therapy. Propolis is a very promising source of natural substances that show a wide range of pharmacological properties, including antifungal activity against various fungal strains. The purpose of the literature review was to summarize recent studies (PubMed, Scopus) on progress in evaluating the antifungal activity of chemically defined propolis extracts. During the selection of studies, only those with results of antifungal activity expressed as minimal inhibitory concentration (MIC) and/or minimal fungicidal concentration (MFC) were analyzed. Moreover, plant, animal and environmental factors influencing the chemical composition of propolis are discussed. Mechanisms of antifungal activity of propolis extracts and research trends in the aspect of developing new therapies and the assessment of drug interactions are indicated. The review of the research results shows that there is great progress in the definition of propolis extracts. After comparing the MIC/MFC values, it was assessed that propolis extracts offer a wide range of activity not only against pathogenic Candida strains but also against risky molds; however, the strength of this activity is varied.
The 30-kDa family of lipoproteins from insect hemolymph has been the focus of a number of studies over the last few years. Recently, four crystal structures of Bombyx mori lipoprotein 7 have been determined. Here we report two crystal structures of another member of the 30-kDa lipoprotein family, Bombyx mori lipoprotein 3 (Bmlp3). The protein was isolated from its natural source, mulberry silkworm hemolymph. It crystallized in two different crystal forms, Bmlp3-p21 (space group P21) and Bmlp3-c2 (space group C2). The crystal structures were solved by molecular replacement using the coordinates of Bmlp7 as a starting model. The crystals of Bmlp3-p21 diffracted X-rays to 2.4 Å resolution and of Bmlp3-c2 to 2.1 Å resolution. Bmlp3 has an overall fold characteristic of 30-kDa lipoproteins, with a VHS-type N-terminal domain and β-trefoil C-terminal domain. Structural comparison of Bmlp3 and Bmlp7 shows that the loops present in the C-terminal domain are flexible and participate in dimer formation. Additionally, new putative binding sites of Bmlp3 have been analyzed in detail and the electrostatic potential of the protein surface at physiological pH 7.4 conditions has been calculated. The results of these calculations are the starting point for an explanation of the recently reported cell-penetrating properties of the 30-kDa lipoproteins.
The first crystal structure of a complex formed by two storage proteins, SP2 and SP3, isolated from their natural source, mulberry silkworm (Bombyx mori L.) haemolymph, has been determined. The structure was solved by molecular replacement using arylphorin, a protein rich in aromatic amino-acid residues, from oak silkworm as the initial model. The quality of the electron-density maps obtained from the X-ray diffraction experiment allowed the authors to detect that the investigated crystal structure was composed of two different arylphorins: SP2 and SP3. This discovery was confirmed by N-terminal sequencing. SP2 has been extensively studied previously, whereas only a few reports on SP3 are available. However, to date no structural studies have been reported for these proteins. These studies revealed that SP2 and SP3 exist in the silkworm body as a heterohexamer formed by one SP2 trimer and one SP3 trimer. The overall fold, consisting of three haemocyanin-like subdomains, of SP2 and SP3 is similar. Both proteins contain a conserved N-glycosylation motif in their structures.
In 2006 Institute of Natural Fibres and Medicinal Plants (INF&MP) began research on an old Polish cultivar of white mulberry-"Żółwińska". By that time in Europe the white mulberry had been forgotten or known only as a plant associated with breeding of mulberry silkworms. Nevertheless, the initial studies have shown great potential of this plant in energy, food and pharmaceutical industries. The leaves and fruits contain very valuable active substances, which may be used in health care. What is more, very fast growth of mulberry causes that biomass of the plant may be used as biofuel. The aim of the article is promoting the white mulberry and presenting its possible various uses, which may be very useful for several sectors of the European economy.
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