Increased dynamics in the 40-57 Ω-loop of the G41S variant of human cytochrome c promote its pro-apoptotic conformation

Thrombocytopenia 4 is an inherited autosomal dominant thrombocytopenia, which occurs due to mutations in the human gene for cytochrome c that results in enhanced mitochondrial apoptotic activity. The Gly41Ser mutation was the first to be reported. Here we report stopped-flow kinetic studies of azide binding to human ferricytochrome c and its Gly41Ser variant, together with backbone amide H/D exchange and 15N-relaxation dynamics using NMR spectroscopy, to show that alternative conformations are kinetically and thermodynamically more readily accessible for the Gly41Ser variant than for the wild-type protein. Our work reveals a direct conformational link between the 40-57 Ω-loop in which residue 41 resides and the dynamical properties of the axial ligand to the heme iron, Met80, such that the replacement of glycine by serine promotes the dissociation of the Met80 ligand, thereby increasing the population of a peroxidase active state, which is a key non-native conformational state in apoptosis

Supramolecular nanoscale systems based on amphiphilic tetramethylensulfonatocalix[4]resorcinarenes and cationic polyelectrolyte with controlled guest molecule binding

<p>The water-soluble tetramethylensulfonatocalix[4]resorcinarene with methyl (<b>C1</b>) and pentyl (<b>C5</b>) substitutes on the lower rim forms colloid nanoscale aggregates with poly(diallyldimethylammonium chloride) (<b>PDDA</b>) in aqueous solutions. The size and stability of nanoparticles depend on concentrations of the components and their ratio in the ‘calixarene-polymer’ system. Ternary supramolecular complexes «polymer–macrocycle–guest molecule L-tryptophan (<b>Trp</b>) in conditions of spontaneous pH (3.80 and 4.78 for <b>C1-PDDA</b> and <b>C5-PDDA</b> systems, respectively) in an aqueous solution and in phosphate buffer (pH 7) were investigated by fluorescence method. The addition of the third component – <b>PDDA –</b> to the «non-aggregated <b>C1</b>–<b>Trp</b>» associates leads to the release of <b>Trp</b> in all studied conditions. The possibility of the «binding–release» process of L-tryptophan in «<b>C5</b>–<b>Trp</b>» associates after <b>PDDA</b> addition in the ternary complex is achieved and controlled by the structure of the macrocyclic self-associates and pH conditions.</p

Formation of cooperative amidoaminocalixresorcinarene – methotrexate nanosized aggregates in an aqueous solution and on the surface of gold nanoparticles

<p>Cooperative nanoscale associates of amido(dimethylamino) calixresorcinarenes with pentyl (<b>C5</b>) and undecyl (<b>C11</b>) substituents on lower rim with antitumor drug-methotrexate (<b>MTX</b>) in aqueous solution and on the surface of gold nanoparticles <b>C5</b>@Au and <b>C11</b>@Au were formed. The formation of nanoparticles was investigated by ¹H NMR, NMR FT-PGSE, 2D NOESY, DLS, TEM, spectrophotometry, fluorimetry. It was found that during the interaction of <b>C5</b> or <b>C11</b> macrocycles with <b>MTX</b> in aqueous solution, the latter generates dissociation of macrocycles self-associates with formation of cooperative macrocycle–<b>MTX</b> associates of smaller size due to multiple non-covalent interactions, which leads to increase in fluorescence intensity of <b>MTX</b>. In contrast, binding of <b>MTX</b> by macrocyclic associates preorganized as bilayer on surface of gold nanoparticles through electrostatic interactions induces aggregation of <b>C5</b>@Au-<b>MTX</b> or <b>C11</b>@Au-<b>MTX</b> associates, which results in quenching of <b>MTX</b> fluorescence in solution. Such particles have possible potential in the field of binding and delivery of antitumor drugs.</p