Border Biomedical Research Center and Department of Biological Sciences, University of Texas at El Paso, El Paso, TX 79968, USA.
Department of Chemistry and Biochemistry, Kettering University, Flint, MI 48504, USA.
Int J Mol Sci. 2019 Oct 28;20(21):5346. doi: 10.3390/ijms20215346.
Previous studies demonstrated that the 52-kDa FK506-binding protein (FKBP52) proline-rich loop is functionally relevant in the regulation of steroid hormone receptor activity. While zebra fish () FKBP52 contains all of the analogous domains and residues previously identified as critical for FKBP52 potentiation of receptor activity, it fails to potentiate activity. Thus, we used a cross-species comparative approach to assess the residues that are functionally critical for FKBP52 function. Random selection of gain-of-function DrFKBP52 mutants in identified two critical residues, alanine 111 (A111) and threonine 157 (T157), for activation of receptor potentiation by DrFKBP52. In silico homology modeling suggests that alanine to valine substitution at position 111 in DrFKBP52 induces an open conformation of the proline-rich loop surface similar to that observed on human FKBP52, which may allow for sufficient surface area and increased hydrophobicity for interactions within the receptor-chaperone complex. A second mutation in the FKBP12-like domain 2 (FK2), threonine 157 to arginine (T157R), also enhanced potentiation, and the DrFKBP52-A111V/T157R double mutant potentiated receptor activity similar to human FKBP52. Collectively, these results confirm the functional importance of the FKBP52 proline-rich loop, suggest that an open conformation on the proline-rich loop surface is a predictor of activity, and highlight the importance of an additional residue within the FK2 domain.
先前的研究表明，FK506 结合蛋白（FKBP52）富含脯氨酸的环中的 52kDa 结构域在调节甾体激素受体活性方面具有功能相关性。尽管斑马鱼 FKBP52 含有先前被鉴定为增强 FKBP52 受体活性所必需的类似结构域和残基，但它不能增强活性。因此，我们使用跨物种比较的方法来评估对 FKBP52 功能至关重要的残基。在 中随机选择功能获得性 DrFKBP52 突变体，鉴定出两个关键残基，丙氨酸 111（A111）和苏氨酸 157（T157），它们对于 DrFKBP52 激活受体增强作用至关重要。计算机同源建模表明，DrFKBP52 中第 111 位丙氨酸到缬氨酸的取代诱导富含脯氨酸的环表面呈现开放构象，类似于在人 FKBP52 中观察到的构象，这可能允许足够的表面积和增加的疏水性，以利于受体-伴侣复合物内的相互作用。FKBP12 样结构域 2（FK2）中的第二个突变，苏氨酸 157 到精氨酸（T157R），也增强了增强作用，DrFKBP52-A111V/T157R 双突变体增强受体活性类似于人 FKBP52。总之，这些结果证实了 FKBP52 富含脯氨酸的环的功能重要性，表明富含脯氨酸的环表面的开放构象是活性的预测因子，并强调 FK2 结构域内的另一个残基的重要性。
