结晶肌动蛋白管。III. 钪和钇与骨骼肌肌动蛋白的相互作用。

Crystalline actin tubes. III. The interaction of scandium and yttrium with skeletal muscle actin.

作者信息

Barden J A, Curmi P M, Dos Remedios C G

出版信息

Biochim Biophys Acta. 1981 Nov 30;671(1):25-32. doi: 10.1016/0005-2795(81)90089-1.

Abstract

The effect of the trivalent cations scandium (Sc3+) and yttrium (Y3+) on the conformation of G-actin was examined using ultraviolet difference and high resolution 1H-NMR spectroscopy. A comparison was made with data obtained previously with the trivalent lanthanide cations (Ln3+). These results indicate that the first and subsequent Y ions (ionic radius 101.9 pm) behave exactly like Ln3+. Sc3+ is a smaller ion (87 pm) than any of the Ln3+. The first Sc3+ binds to a site on actin that is inaccessible to Mg2+, Y3+ and Ln3+. However, the second Sc3+ to bind behaves like an Ln3+. On replacing the native divalent cation (Mg2+), both Y3+ and Sc3+ mobilize the adenine ring of ATP bound to actin, thus exposing underlying residues to the solvent. When Y3+ and Sc3+ saturate their binding sites on actin, and when the ionic strength is raised to 0.1 M with KCl at pH 6.9, the actin aggregates. Y3+ binds to actin with a ratio of 6 : 1 and induces the aggregation of actin into crystalline actin tubes, whilst Sc3+ binds with a ratio of 8 : 1 and induces amorphous actin aggregates. These results are consistent with the suggestion that actin tubes are induced by trivalent cations, principally on the basis of their binding stoichiometry, which is determined by ionic radius.

摘要

利用紫外差光谱和高分辨率¹H-NMR光谱研究了三价阳离子钪（Sc³⁺）和钇（Y³⁺）对G-肌动蛋白构象的影响。并与先前用三价镧系阳离子（Ln³⁺）获得的数据进行了比较。这些结果表明，第一个及后续的Y离子（离子半径101.9皮米）的行为与Ln³⁺完全相同。Sc³⁺是比任何Ln³⁺都小的离子（87皮米）。第一个Sc³⁺结合到肌动蛋白上一个Mg²⁺、Y³⁺和Ln³⁺无法接近的位点。然而，第二个结合的Sc³⁺的行为类似于Ln³⁺。当取代天然二价阳离子（Mg²⁺）时，Y³⁺和Sc³⁺都会使与肌动蛋白结合的ATP的腺嘌呤环移动，从而使潜在的残基暴露于溶剂中。当Y³⁺和Sc³⁺饱和它们在肌动蛋白上的结合位点，并且当在pH 6.9用KCl将离子强度提高到0.1 M时，肌动蛋白会聚集。Y³⁺以6:1的比例与肌动蛋白结合，并诱导肌动蛋白聚集成结晶状的肌动蛋白管，而Sc³⁺以8:1的比例结合并诱导形成无定形的肌动蛋白聚集体。这些结果与以下观点一致，即肌动蛋白管主要是由三价阳离子根据其结合化学计量比诱导形成的，而结合化学计量比由离子半径决定。