Magnesium binding to yeast ribosomes

Walters, J. A. L. I.; Os, G.A.J. Van

doi:10.1002/bip.360100103

Cited by 17 publications

(8 citation statements)

References 9 publications

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“…If one assumes that (i) Donnan equilibrium is negligible at low ionic strength, (ii) if binding occurs, Na+ or K+ ions bind to equivalent sites, and (iii) the Debye-Hiickel effect would be insignificant, analysis of the data showed that reduction in spermidine binding could not be accounted for by competitive inhibition by Na+ or K+ ions. This finding is consistent with earlier studies (Walters & Van Os, 1971; Krakauer, 1974;Stein & Crothers, 1976) stating that monovalent cations do not compete effectively with divalent cations for binding sites on polynucleotides.…”

Section: Since X = Etsupporting

confidence: 93%

Binding of spermidine to transfer ribonucleic acid

McMahon¹,

Erdmann²

1982

Biochemistry

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The binding of spermidine to yeast tRNAPhe and Escherichia coli tRNAGlu2 at low and high ionic strength was studied by equilibrium dialysis. Once corrected for the expected Donnan effect, the binding at low ionic strength obeys the simple relationship of equivalent binding sites, and cooperative binding of spermidine to tRNA could not be detected. At low ionic strength (0.013 M Na+ ion), tRNAPhe (yeast) has 13.9 +/- 2.3 strong spermidine binding sites per molecule with Kd = 1.39 X 10(-6) M and a few weak spermidine binding sites which were inaccessible to experimentation; tRNAGlu2 (E. coli) has 14.8 +/- 1.6 strong spermidine binding sites and 4.0 +/- 0.1 weak spermidine binding sites with Kd = 1.4 X 10(-6) M and Kd = 1.23 X 10(-4) M, respectively. At high ionic strength (0.12 M monovalent cation) and 0.01 M Mg2+, tRNAPhe (yeast) has approximately 13 strong spermidine binding sites with an apparent Kd = 3.4 X 10(-3) M while the dimeric complex tRNAPhe X tRNAGlu2 has 10.4 +/- 1.2 strong spermidine binding sites per monomer with an apparent Kd = 2.0 X 10(-3) M. In the presence of increasing Na+ ion or K+ ion concentration, spermidine binding data do not fit a model for competitive binding to tRNA by monovalent cations. Rather, analysis of binding data by the Debye-Hückel approximation results in a good fit of experimental data, indicating that monovalent cations form a counterion atmosphere about tRNA, thus decreasing electrostatic interactions. On the basis of equilibrium binding analyses, it is proposed that the binding of spermidine to tRNA occurs predominantly by electrostatic forces.

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Section: Since X = Etsupporting

confidence: 93%

Binding of spermidine to transfer ribonucleic acid

McMahon¹,

Erdmann²

1982

Biochemistry

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“…This reduction in the electrostatic repulsion between the subunits would allow association. The studies of Walters & Van Os (1970, 1971 on yeast ribosomes and Wishnia & Boussert (1977) on E. coli ribosomes support the electrostatic model. Calculations by these groups also showed that the reduction of the electrostatic repulsion by Mg2+ theoretically is sufficient to promote subunit association.…”

mentioning

confidence: 52%

Influence of various cations on the equilibriums between wheat germ ribosomes and their subunits

Sperrazza¹,

Moore²,

Spremulli³

1981

Biochemistry

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The influence of alkaline earth metal ions, alkali metal ions, ammonium ions, and polyamines upon the equilibria between high-salt-washed wheat germ ribosomes and their subunits was investigated by light scattering. The Mgz+-dependent, reversible association of ribosomal subunits was studied with buffers containing 100 mM concentrations of the chloride salts of various monovalent cations. These studies indicate that K+ and Na+ are most effective in dissociating the ribosomes into subunits, followed by Rb+ and then NH4+. The dissociation curves determined with buffers containing K+, Na', Rb', and NH4+ ions exhibit [Mg"] 1/2 values of 1.4, 1.4, 1.2, and 0.7 mM, respectively. The divalent cations, in general, strongly promote subunit association but differ in their abilities to do so. Ca2+ associates the ribosomal subunits more effectively than Sr2+, which is more effective than Mgz+. In the presence of 100 mM KCl and 0.15 mM MgClz, Ca2+-, Sr2+-, and Mgz+-dependent association curvesx e subunits of both eucaryotic and procaryotic ribosomes are capable of reversible association and dissociation. The types and concentrations of various cations present play a major role in determining the position of the equilibrium between the intact ribosome and its subunits. Kinetic, thermodynamic, and ion-specificity studies have been performed with Escherichia coli ribosomes in an effort to explain the roles of MgZ+, K+, and polyamines in the association of the subunits. Conflicting mechanisms have been proposed as a result of these studies. One model suggests that Mgz+ binds to specific sites on the subunits and thereby promotes subunit association (Petermann, 1964;Goldberg, 1966). This model is supported by the data of Zitomer & Flab (1972), who found that MgZ+, Ca2+, and polyamines promote ribosomal subunit association while K+ promotes subunit dissociation. Ca2+, however, was less effective than Mg2+ in promoting subunit association, suggesting that the ions were acting at specific sites. In contrast, the electrostatic model suggests that Mg2+ neutralizes the charged groups on the ribosomal subunits. This reduction in the electrostatic repulsion between the subunits would allow association. The studies of Walters & Van Os (1970, 1971) on yeast ribosomes and Wishnia & Boussert (1977) on E . coli ribosomes support the electrostatic model. Calculations by these groups also showed that the reduction of the electrostatic repulsion by Mg2+ theoretically is sufficient to promote subunit association. Nieuwenhuysen et al. (1980), using Artemia salina ribosomes, have shown that the molar volume changes produced by ribosomal subunit association are similar to those observed with E. coli type A ribosomes. Furthermore, they have suggested that this large volume change is consistent with two From the exhibit [M2+lIl2 values of 0.9, 1.1, and 1.4 mM, respectively. The abilities of the polyamines to associate ribosomal subunits in buffers containing 100 mM KCl and 0.20 mM MgClz were investigated. Both spermine ( [~p m ]~/~ = 0.09 mM) and sp...

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“…An interpretation in molecular terms of the finding that Mg2+ is released from ribosomes in the pH range from 5 to 3 is difficult to make because some of the purine and pyrimidine nitrogens of RNA bases are titrated in this range along with protein carboxyl groups. Apparently, Mg2+ can bind to all of the phosphate groups in the RNA of ribosomes (21); two reactions seem to be involved, one with a pK(Mg2+) of 3.8 and one with a pK(Mg2+) of 2.2. Our titration results indicate that the need for Mg2+ to neutralize negatively charged groups in ribosomes is reduced below pH 5, and so there must be increased internal neutralization between phosphate groups and positively charged bases in RNA molecules.…”

mentioning

confidence: 99%

Acid-Base Titration of Streptococci and the Physical States of Intracellular Ions

Marquis

Porterfield

Matsumura

1973

Journal of Bacteriology

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Acid titrations of intact and butanol-treated cells of Streptococcus faecalis revealed that nearly all of the intracellular K + ions could diffuse into the suspending medium in association with small anions, including ribonucleic acid breakdown products, when the cell membrane was damaged. In contrast, nearly all of the intracellular Mg 2+ ions appeared to be firmly bound to stable internal cell components but could be displaced reversibly by hydronium ions. The cell membrane acted as a barrier to ion movements, and Mg 2+ displacement from intact cells required more acid conditions, by as much as 2.5 pH units, than did displacement from butanol-damaged cells. Some 15 to 20% of the cell magnesium appeared to be associated with surface structures in that it could be removed at pH 7 with ethylenediaminetetraacetic acid or displaced by Co 2+ , Ni 2+ , Sr 2+ , or La 3+ . Magnesium could be displaced from isolated cell walls and membranes by hydronium ions in the pH range from 5 to 3, over which carboxyl groups were titrated. Displacement of magnesium from ribosomes also took place between pH 5 and 3, but it was more difficult to identify the magnesium-releasing groups because both protein carboxyl groups and purine and pyrimidine ring nitrogens can become protonated in this pH range. Isolated protoplast membranes remained structurally intact when completely depleted of magnesium. Furthermore, protoplasts isolated from intact cells were found to have greatly enhanced resistance to osmotic shock in acid media, even when solute loss was not extensive. Osmotic resistance was lost when the protoplasts were again placed in neutral media, and this reversibility suggested that acidification caused changes in the physical properties of membranes as well as solute leakage from cells.

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Magnesium binding to yeast ribosomes

Cited by 17 publications

References 9 publications

Binding of spermidine to transfer ribonucleic acid

Binding of spermidine to transfer ribonucleic acid

Influence of various cations on the equilibriums between wheat germ ribosomes and their subunits

Acid-Base Titration of Streptococci and the Physical States of Intracellular Ions

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