No abstract

Blad polypeptide comprises residues 109–281 of Lupinus albus β-conglutin precursor. It occurs naturally as a major subunit of an edible, 210 kDa oligomer which accumulates to high levels, exclusively in the cotyledons of Lupinus seedlings between the 4th and 14th day after the onset of germination. Blad-containing oligomer (BCO) exhibits a potent and broad spectrum fungicide activity toward plant pathogens and is now on sale in the US under the tradename FractureTM. In this work we demonstrate its antifungal activity toward human pathogens and provide some insights on its mode of action. BCO bioactivity was evaluated in eight yeast species and compared to that of amphotericin B (AMB). BCO behaved similarly to AMB in what concerns both cellular inhibition and cellular death. As a lectin, BCO binds strongly to chitin. In addition, BCO is known to possess ‘exochitinase’ and ‘endochitosanase’ activities. However, no clear disruption was visualized at the cell wall after exposure to a lethal BCO concentration, except in cell buds. Immunofluorescent and immunogold labeling clearly indicate that BCO enters the cell, and membrane destabilization was also demonstrated. The absence of haemolytic activity, its biological origin, and its extraordinary antifungal activity are the major outcomes of this work, and provide a solid background for a future application as a new antifungal therapeutic drug. Furthermore, its predictable multisite mode of action suggests a low risk of inducing resistance mechanisms, which are now a major problem with other currently available antifungal drugs.

No abstract

Full length and truncated human Endonuclease III/hNTH1 possess distinct conformations, redox properties and interactions with the damaged DNA substrate.

Iron is a vital element for life. However, after the Great Oxidation Event, the bioavailability of this element became limited. To overcome iron shortage and to scavenge this essential nutrient, microorganisms use siderophores, secondary metabolites that have some of the highest affinities for ferric iron. The crucial step of iron release from these compounds to be subsequently integrated into cellular components is mediated by Siderophore-Interacting Proteins (SIPs) or Ferric-siderophore reductases (FSRs). In this work, we report the structure of an FSR for the first time. FhuF from laboratory strain Escherichia coli K-12 is the archetypical FSR, known for its atypical 2Fe-2S cluster with the binding motif C-C-X10-C-X2-C. The 1.9 A resolution crystallographic structure of FhuF shows it to be the only 2Fe-2S protein known to date with two consecutive cysteines binding different Fe atoms. This novel coordination provides a rationale for the unusual spectroscopic properties of FhuF. Furthermore, FhuF shows an impressive ability to reduce hydroxamate-type siderophores at very high rates when compared to flavin-based SIPs, but like SIPs it appears to use the redox-Bohr effect to achieve catalytic efficiency. Overall, this work closes the knowledge gap regarding the structural properties of ferric-siderophore reductases and simultaneously opens the door for further understanding of the diverse mechanistic abilities of these proteins in the siderophore recycling pathway.