THE INTERACTION OF FLAVINS WITH EGG-WHITE RIBOFLAVIN-BINDING PROTEIN
THE INTERACTION OF FLAVINS WITH EGG-WHITE RIBOFLAVIN-BINDING PROTEIN
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DOI：
10.1016/0003-9861(80)90005-3
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发表时间：
1980-01-01
影响因子：
3.9
通讯作者：
MCCORMICK, DB
中科院分区：
文献类型：
--
作者：
CHOI, JD;MCCORMICK, DB
通过黄素类似物与蛋清核黄素结合蛋白结合常数的测定，以及游离和结合黄素吸收光谱的变化，阐明了蛋清核黄素结合蛋白中核黄素结合部位的性质。光谱的变化和蛋白质与带电物种的不利相互作用表明，全蛋白中的黄素环境是疏水的。黄素的环或侧链部分的修饰通常会导致结合能的降低。虽然结构中没有一个是必需的，但7-和8-甲基以及2‘’-羟基对结合作用的贡献最大。异四氧嘧啶在C-2和N-3区域的结合位置对取代基的相对位置不敏感，相对开放，而在C-8，N-10，特别是C-1‘’和4-羰基位置有相当大的空间限制。N-10侧链的羟基通过形成氢键以立体选择性的方式贡献。对只代表黄素部分的模型化合物的研究表明，环的类二甲苯部分参与了结合的初级相互作用，并相对埋藏在蛋白质中。结合时蛋白质荧光的猝灭主要是由于结合部位的酪氨基残基与喹恶啉部分之间的基态堆积作用，而不是由于Foerster能量转移。
The properties of the riboflavin-binding site in the riboflavin-binding protein from egg white were elucidated by determining constants for binding of flavin analogs to the protein and by changes in absorption spectra of free and bound flavins. The spectral changes and unfavorable interaction of the protein with charged species indicate that the overall flavin environment in the holoprotein is hydrophobic. Modification of either ring or side-chain portions of flavin usually results in a decrease of binding energy. Although no one portion of the structure is essential, both 7- and 8-methyl groups and 2''-hydroxyl group contribute most significantly to binding. The binding site at the region of C-2 and N-3 of the isoalloxazine is insensitive to the relative site of a substituent and relatively open, whereas considerable steric limitation is imposed at C-8, N-10, especially C-1'' and 4-carbonyl positions. The hydroxyl groups of the N-10 side chain contribute in a stereoselective manner by formation of H-bonds. Studies with model compounds that represent only a part of flavin indicate that the dimethylbenzenoid portion of the ring is involved in primary interactions of binding, and relatively buried in the protein. The quenching of protein fluorescence upon binding is mainly due to ground-state stacking interaction between a trytophanyl residue at the binding site and quinoxaline portion, not to Foerster energy transfer.