It has been shown previously, using G-actin labeled with N-iodoacetyl-N'-(5-sulfo-1-naphthyl)ethylene-diamine, that Mg2+ induces a conformational change in monomeric G-actin as a consequence of binding to a tight divalent cation binding site (Frieden, C. (1982) J. Biol. Chem. 257, 2882-2886). Using the same fluorescent probe, we show that, subsequent to the Mg2+-induced conformational change, c...

The effects of Mg2+ on thermophilic (55°C) granules grown on acetate in 0.2-liter upflow anaerobic sludge blanket reactors were studied. The methanogens in the granules were identified and counted by using antibody probes and the antigenic fingerprinting method. Packets of large coccoidal cells antigenically related to Methanosarcina thermophila TM-1 were scarce in the absence of Mg2' but incre...

Actin-activated ATP hydrolysis by phosphorylated arterial myosin is Ca2+-dependent at Mg2+ concentrations which allow myosin to bind 2 mol of Ca2+ per mol (S. Chacko and A. Rosenfeld (1982) Proc. Natl. Acad. Sci. U. S. A. 79, 292-296). The possible effects of myosin filament formation and conformational change involving the rod portion of the myosin molecule on actin-myosin interaction and acti...

The study of pollution due to combined antibiotics and metals is urgently needed. Photochemical processes are an important transformation pathway for antibiotics in the environment. The mechanisms underlying the effects of metal-ion complexation on the aquatic photochemical transformation of antibiotics in different dissociation forms are crucial problems in science, and beg solutions. Herein, ...

Ca2+-stimulated Mg2+-dependent ATPase (Ca2+ + Mg2+-ATPase) stimulated by calmodulin, by partial proteolysis or by oleic acid in erythrocyte membranes was inhibited by various derivatives of the naturally occurring alkaloid berbamine. The ability of these derivatives to inhibit trypsin-activated Ca2+ + Mg2+-ATPase correlated well with their ability to inhibit the calmodulin-stimulated enzyme. In...

The reversibility of the reaction catalyzed by purified (Ca2+ + Mg2+)-dependent ATPase of sarcoplasmic reticulum was studied by measuring the rates of synthesis and hydrolysis of ATP observed during the ATP in equilibrium Pi exchange reaction. The ratio between the velocities of hydrolysis and synthesis of ATP was found to vary between 700 and 1.2 depending on the concentrations of ATP, Pi, Mg2...

We have analysed, with the aid of a novel radioiodinated oxytocin (OT)-receptor antagonist, the role of Mg2+ in uterine OT-receptor function. The antagonist-receptor interaction was characterized by high affinity, reversibility and stereospecificity in Tris/HCl buffer containing 3 mmol of Mg2+/litre as well as buffer free of Mg2+. By contrast, omission of Mg2+ decreased the affinity of the rece...

The ability of excess Mg2+ to compensate the absence of cell wall related genes in Bacillus subtilis has been known for a long time, but the mechanism has remained obscure. Here, we show that the rigidity of wild-type cells remains unaffected with excess Mg2+ , but the proportion of amidated meso-diaminopimelic (mDAP) acid in their peptidoglycan (PG) is significantly reduced. We identify the am...

The S4 transmembrane segment is the primary voltage sensor in voltage-dependent ion channels. Its movement in response to changes in membrane potential leads to the opening of the activation gate, which is formed by a separate structural component, the S6 segment. Here we show in voltage-, Ca2+-, and Mg2+-dependent, large conductance K+ channels that the S4 segment participates not only in volt...

Binding of metal ions is an important factor governing the folding and dynamics of RNA. Shielding of charges in the polyanionic backbone allows RNA to adopt a diverse range of folded structures that give rise to their many functions within the cell. Some RNA sequences fold only in the presence of Mg2+, which may be bound via direct interactions or occupy the more diffuse "ion atmosphere" around...