New Aspects of Uptake and Metabolism of Non-organic and Organic Iodine Compounds-The Role of Vanadium and Plant-Derived Thyroid Hormone Analogs in Lettuce.

The process of uptake and translocation of non-organic iodine (I) ions, I- and IO3 -, has been relatively well-described in literature. The situation is different for low-molecular-weight organic aromatic I compounds, as data on their uptake or metabolic pathway is only fragmentary. The aim of this study was to determine the process of uptake, transport, and metabolism of I applied to lettuce plants by fertigation as KIO3, KIO3 + salicylic acid (KIO3+SA), and iodosalicylates, 5-iodosalicylic acid (5-ISA) and 3,5-diiodosalicylic acid (3,5-diISA), depending on whether additional fertilization with vanadium (V) was used. Each I compound was applied at a dose of 10 µM, SA at a dose of 10 µM, and V at a dose of 0.1 µM. Three independent 2-year-long experiments were carried out with lettuce; two with pot systems using a peat substrate and mineral soil and one with hydroponic lettuce. The effectiveness of I uptake and translocation from the roots to leaves was as follows: 5-ISA > 3,5-diISA > KIO3. Iodosalicylates, 5-ISA and 3,5-diISA, were naturally synthesized in plants, similarly to other organic iodine metabolites, i.e., iodotyrosine, as well as plant-derived thyroid hormone analogs (PDTHA), triiodothyronine (T3) and thyroxine (T4). T3 and T4 were synthesized in roots with the participation of endogenous and exogenous 5-ISA and 3,5-diISA and then transported to leaves. The level of plant enrichment in I was safe for consumers. Several genes were shown to perform physiological functions, i.e., per64-like, samdmt, msams5, and cipk6.

Crystal structures of serum albumins from domesticated ruminants and their complexes with 3,5-diiodosalicylic acid.

Serum albumin (SA) is the most abundant protein in plasma and is the main transporter of molecules in the circulatory system of all vertebrates, with applications in medicine, the pharmaceutical industry and molecular biology. It is known that albumins from different organisms vary in sequence; thus, it is important to know the impact of the amino-acid sequence on the three-dimensional structure and ligand-binding properties. Here, crystal structures of ovine (OSA) and caprine (CSA) serum albumins, isolated from sheep and goat blood, are described, as well those of their complexes with 3,5-diiodosalicylic acid (DIS): OSA-DIS (2.20 Šresolution) and CSA-DIS (1.78 Šresolution). The ligand-free OSA structure was determined in the trigonal space group P3221 at 2.30 Šresolution, while that of CSA in the orthorhombic space group P212121 was determined at 1.94 Šresolution. Both albumins are also capable of crystallizing in the triclinic space group P1, giving isostructural crystals that diffract to around 2.5 Šresolution. A comparison of OSA and CSA with the closely related bovine serum albumin (BSA) shows both similarities and differences in the distribution of DIS binding sites. The investigated serum albumins from domesticated ruminants in their complexes with DIS are also compared with the analogous structures of equine and human serum albumins (ESA-DIS and HSA-DIS). Surprisingly, despite 98% sequence similarity, OSA binds only two molecules of DIS, whereas CSA binds six molecules of this ligand. Moreover, the binding of DIS to OSA and CSA introduced changes in the overall architecture of the proteins, causing not only different conformations of the amino-acid side chains in the binding pockets, but also a significant shift of the whole helices, changing the volume of the binding cavities.

Crystallographic studies of the complexes of bovine and equine serum albumin with 3,5-diiodosalicylic acid.

Due to their extraordinary binding properties, serum albumins are the main transporters of many small molecules in the circulatory system. Although all mammalian serum albumins exhibit quite high sequence similarity, their binding abilities are not the same. Until now, only human serum albumin (HSA) was subjected to extensive structural studies in complexes with various ligands. Here we present two crystal structures of the complexes of equine and bovine serum albumins with 3,5-diiodosalicylic acid (DIS), at resolutions 2.12 Å and 2.65 Å, respectively, and analyze interactions of the DIS ligand with both macromolecules. We highlight the differences in distribution of DIS binding sites between the bovine and equine serum albumins and compare results with the HSA binding ability of DIS and other structurally similar ligands.