Conversion of human alpha-lactalbumin to an apo-like state in the complexes with basic poly-amino acids: toward understanding of the molecular mechanism of antitumor action of HAMLET.
Conversion of human alpha-lactalbumin to an apo-like state in the complexes with basic poly-amino acids: toward understanding of the molecular mechanism of antitumor action of HAMLET.
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DOI：
10.1021/pr0497778
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发表时间：
2005-02
影响因子：
4.4
通讯作者：
S. Permyakov;Irina V Pershikova;Andrei P Zhadan;J. Goers;Anush Bakunts;V. Uversky;L. Berliner;E. Permyakov
中科院分区：
文献类型：
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作者：
S. Permyakov;Irina V Pershikova;Andrei P Zhadan;J. Goers;Anush Bakunts;V. Uversky;L. Berliner;E. Permyakov
最近显示与油酸相关的α-乳白蛋白（哈姆雷特）与核心组蛋白相互作用，从而引发肿瘤细胞的凋亡（J. Biol. Chem. 2003，278，42131）。在先前的工作中，我们揭示了在不存在脂肪酸的情况下单体α-乳白蛋白也可以与组蛋白相互作用，并且此外，与代表组蛋白蛋白的简单模型的碱性聚氨基酸（聚-Lys和聚-Arg）相互作用（Biochemistry 2004，43，5575）。α-乳白蛋白与组蛋白或聚赖氨酸（Arg）的结合基本上改变了其性质。本文采用稳态荧光、圆二色性和差示扫描量热法研究了α-乳清蛋白与聚赖氨酸（Arg）复合后的结构性质和构象稳定性的变化。复合物的形成强烈依赖于离子强度，证实了其静电性质。用各种分子量的聚氨基酸进行的实验证明，每个聚赖氨酸（Arg）结合的α-乳白蛋白分子的数量与聚氨基酸无规卷曲的表面积之间成正比。聚氨基酸与Ca 2+饱和的人α-乳白蛋白的结合将其热稳定性降低至其游离apo形式的水平，并将Ca 2+亲和力降低4个数量级。α-乳白蛋白与聚赖氨酸（Arg）的复合物（称为聚氨基酸修饰的α-乳白蛋白（兰帕））的构象状态不同于迄今为止表征的所有其他α-乳白蛋白状态，代表对钙离子具有显著降低的亲和力的apo样（熔融球状）状态。α-乳清蛋白有效转化为兰帕状态的要求是由几十个氨基酸残基组成的聚赖氨酸（Arg）链。
It was recently shown that alpha-lactalbumin associated with oleic acid (HAMLET) interacts with core histones thereby triggering apoptosis of tumor cells (J. Biol. Chem. 2003, 278, 42131). In previous work, we revealed that monomeric alpha-lactalbumin in the absence of fatty acids can also interact with histones and, moreover, with basic poly-amino acids (poly-Lys and poly-Arg) that represent simple models of histone proteins (Biochemistry 2004, 43, 5575). Association of alpha-lactalbumin with histone or poly-Lys(Arg) essentially changes its properties. In the present work, the character of the changes in structural properties and conformational stability of alpha-lactalbumin in the complex with poly-Lys(Arg) has been studied in detail by steady-state fluorescence, circular dichroism, and differential scanning calorimetry. Complex formation strongly depends on ionic strength, confirming its electrostatic nature. Experiments with the poly-amino acids of various molecular masses demonstrated a direct proportionality between the number of alpha-lactalbumin molecules bound per poly-Lys(Arg) and the surface area of the poly-amino acid random coil. The binding of the poly-amino acids to Ca2+-saturated human alpha-lactalbumin decreases its thermal stability down to the level of its free apo-form and decreases Ca2+-affinity by 4 orders of magnitude. The conformational state of alpha-lactalbumin in a complex with poly-Lys(Arg), named alpha-LActalbumin Modified by Poly-Amino acid (LAMPA), differs from all other alpha-lactalbumin states characterized to date, representing an apo-like (molten globule-like) state with substantially decreased affinity for calcium ion. The requirement for efficient conversion of alpha-lactalbumin to the LAMPA state is a poly-Lys(Arg) chain consisting of several tens of amino acid residues.