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首页> 外文期刊>Biochemistry >Relative role of anions and cations in the stabilization of halophilic malate dehydrogenase.
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Relative role of anions and cations in the stabilization of halophilic malate dehydrogenase.

机译：阴离子和阳离子在嗜盐苹果酸脱氢酶稳定中的相对作用。

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Halophilic malate dehydrogenase unfolds at low salt, and increasing the salt concentration stabilizes, first, the folded form and then, in some cases, destabilizes it. From inactivation and fluorescence measurements performed on the protein after its incubation in the presence of various salts in a large range of concentrations, the apparent effects of anions and cations were found to superimpose. A large range of ions was examined, including conditions that are in general not of physiological relevance, to explore the physical chemistry driving adaptation to extreme environments. The order of efficiency of cations and anions to maintain the folded form is, for the low-salt transition, Ca(2+) approximately Mg(2+) > Li(+) approximately NH(4)(+) approximately Na(+) > K(+) > Rb(+) > Cs(+), and SO(4)(2)(-) approximately OAc(-) approximately F(-) > Cl(-), and for the high-salt transition, NH(4)(+) approximately Na(+) approximately K(+) approximately Cs(+) > Li(+) > Mg(2+) > Ca(2+), and SO(4)(2)(-) approximately OAc(-) approximately F(-) > Cl(-) > Br(-) > I(-). If a cation or anion is very stabilizing, the effect of the salt ion of opposite charge is limited. Anions of high charge density are always the most efficient to stabilize the folded form, in accordance with the order found in the Hofmeister series, while cations of high charge density are the most efficient only at the lower salt concentrations and tend to denature the protein at higher salt concentrations. The stabilizing efficiency of cations and anions can be related in a minor way to their effect on the surface tension of the solution, but the interaction of ions with sites only present in the folded protein has also to be taken into account. Unfolding at high salt concentrations corresponds to interactions of anions of low charge density and cations of high charge density with the peptide bond, as found for nonhalophilic proteins.
机译：嗜盐的苹果酸脱氢酶在低盐时会解折叠，增加盐浓度会使其稳定，首先是折叠形式，然后在某些情况下使其不稳定。通过在各种浓度范围内的各种盐存在下孵育后对蛋白质进行的灭活和荧光测量，发现阴离子和阳离子的表观作用是叠加的。检查了大范围的离子（包括通常与生理无关的条件），以探索推动对极端环境适应的物理化学。阳离子和阴离子维持折叠形式的效率顺序为：对于低盐过渡，Ca（2+）约Mg（2+）> Li（+）约NH（4）（+）约Na（+ ）> K（+）> Rb（+）> Cs（+），而SO（4）（2）（-）约OAc（-）约F（-）> Cl（-），对于高盐过渡，NH（4）（+）约Na（+）约K（+）约Cs（+）> Li（+）> Mg（2+）> Ca（2+）和SO（4）（2） （-）近似OAc（-）近似F（-）> Cl（-）> Br（-）> I（-）。如果阳离子或阴离子非常稳定，则带相反电荷的盐离子的作用会受到限制。按照Hofmeister系列中的顺序，高电荷密度的阴离子总是最有效的稳定折叠形式，而高电荷密度的阳离子仅在较低的盐浓度下才是最有效的，并且倾向于在低盐浓度下变性蛋白质。更高的盐浓度。阳离子和阴离子的稳定效率可能与它们对溶液表面张力的影响关系不大，但是离子与仅存在于折叠蛋白中的位点之间的相互作用也必须考虑在内。高盐浓度下的解折叠对应于低电荷密度的阴离子和高电荷密度的阳离子与肽键的相互作用，如非嗜盐蛋白所见。

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