国产bbaaaaa片,成年美女黄网站色视频免费,成年黄大片,а天堂中文最新一区二区三区,成人精品视频一区二区三区尤物

首頁> 外文OA文獻 >Thiopurine S-methyltransferase - characterization of variants and ligand binding
【2h】

Thiopurine S-methyltransferase - characterization of variants and ligand binding

機譯：硫嘌呤S-甲基轉移酶-變異體和配體結合的表征

代理獲取
本網(wǎng)站僅為用戶提供外文OA文獻查詢和代理獲取服務，本網(wǎng)站沒有原文。下單后我們將采用程序或人工為您竭誠獲取高質量的原文，但由于OA文獻來源多樣且變更頻繁，仍可能出現(xiàn)獲取不到、文獻不完整或與標題不符等情況，如果獲取不到我們將提供退款服務。請知悉。
  • 摘要
  • 著錄項
  • 相似文獻
  • 相關主題

摘要

Thiopurine S-methyltransferase (TPMT) belongs to the Class I S-adenosylmethionine-dependent methyltransferase (SAM-MT) super family of structurally related proteins. Common to the members of this large protein family is the catalysis of methylation reactions using S-adenosylmethionine (SAM) as a methyl group donor, although SAM-MTs act on a wide range of different substrates and carry out numerous biologically important functions. While the natural function of TPMT is unknown, this enzyme is involved in the metabolism of thiopurines, a class of pharmaceutical substances administered in treatment of immune-related disorders. Specifically, methylation by TPMT inactivates thiopurines and their metabolic intermediates, which reduces the efficacy of clinical treatment and increases the risk of adverse side effects. To further complicate matters, TPMT is a polymorphic enzyme with over 40 naturally occurring variants known to date, most of which exhibit lowered methylation activity towards thiopurines. Consequently, there are individual variations in TPMTmediated thiopurine inactivation, and the administered dose has to be adjusted prior to clinical treatment to avoid harmful side effects. Although the clinical relevance of TPMT is well established, few studies have investigated the molecular causes of the reduced methylation activity of variant proteins. In this thesis, the results of biophysical characterization of two variant proteins, TPMT*6 (Y180F) and TPMT*8 (R215H), are presented. While the properties of TPMT*8 were indistinguishable from those of the wild-type protein, TPMT*6 was found to be somewhat destabilized. Interestingly, the TPMT*6 amino acid substitution did not affect the functionality or folding pattern of the variant protein. Therefore, the decreased in vivo functionality reported for TPMT*6 is probably caused by increased proteolytic degradation in response to the reduced stability of this protein variant, rather than loss of function. Also presented herein are novel methodological approaches for studies of TPMT and its variants. Firstly, the advantages of using 8-anilinonaphthalene-1-sulfonic acid (ANS) to probe TPMT tertiary structure and active site integrity are presented. ANS binds exclusively to the native state of TPMT with high affinity (KD ~ 0.2 μm) and a 1:1 ratio. The stability of TPMT was dramatically increased by binding of ANS, which was shown to co-localize with the structurally similar adenine moiety of the cofactor SAM. Secondly, an enzyme activity assay based on isothermal titration calorimetry (ITC) is presented. Using this approach, the kinetics of 6-MP and 6-TG methylation by TPMT has been characterized.
機譯：硫嘌呤S-甲基轉移酶（TPMT）屬于結構相關蛋白的I類S-腺苷甲硫氨酸依賴性甲基轉移酶（SAM-MT）超家族。該大蛋白家族成員的共同點是使用S-腺苷甲硫氨酸（SAM）作為甲基供體的甲基化反應的催化作用，盡管SAM-MT可以作用于多種不同的底物并具有許多生物學上重要的功能。雖然TPMT的天然功能尚不清楚，但該酶與硫嘌呤的代謝有關，硫嘌呤是一類用于治療免疫相關疾病的藥物。具體而言，TPMT甲基化可使硫嘌呤及其代謝中間體失活，從而降低了臨床治療的效率并增加了不良副作用的風險。進一步使事情復雜化的是，TPMT是一種多態(tài)性酶，迄今已知有40多種天然存在的變體，其中大多數(shù)對硫嘌呤的甲基化活性降低。因此，TPMT介導的硫嘌呤失活存在個體差異，在臨床治療之前必須調(diào)整給藥劑量以避免有害的副作用。盡管TPMT的臨床相關性已得到很好的確立，但很少有研究調(diào)查變異蛋白甲基化活性降低的分子原因。本文提出了兩種變異蛋白TPMT * 6（Y180F）和TPMT * 8（R215H）的生物物理表征結果。 TPMT * 8的特性與野生型蛋白沒有區(qū)別，但發(fā)現(xiàn)TPMT * 6不穩(wěn)定。有趣的是，TPMT * 6氨基酸取代不影響變異蛋白的功能或折疊模式。因此，報道的針對TPMT * 6的體內(nèi)功能性下降可能是由于蛋白水解降解增加而引起的，這是由于該蛋白質變體的穩(wěn)定性降低而不是功能喪失引起的。本文還提供了用于研究TPMT及其變體的新穎方法論方法。首先，介紹了使用8-苯胺基萘-1-磺酸（ANS）探測TPMT的三級結構和活性位點完整性的優(yōu)點。 ANS僅以高親和力（KD?0.2μm）和1：1的比例結合到TPMT的原始狀態(tài)。 TPMT的穩(wěn)定性通過ANS的結合而顯著增加，這表明它與輔助因子SAM的結構相似的腺嘌呤部分共定位。其次，提出了一種基于等溫滴熱法（ITC）的酶活性測定方法。使用這種方法，已經(jīng)表征了通過TPMT進行6-MP和6-TG甲基化的動力學。

著錄項

  • 作者

    Blissing, Annica;

  • 作者單位
  • 年度 2017
  • 總頁數(shù)
  • 原文格式 PDF
  • 正文語種 eng
  • 中圖分類

相似文獻

  • 外文文獻
  • 中文文獻
  • 專利
代理獲取

客服郵箱：kefu@zhangqiaokeyan.com

京公網(wǎng)安備：11010802029741號 ICP備案號：京ICP備15016152號-6 六維聯(lián)合信息科技 (北京) 有限公司?版權所有

  • 客服微信

  • 服務號