化学所成功实现分子马达在蛋白微胶囊表面的组装

在科技部、国家自然科学基金委和中国科学院的支持下,胶体、界面与化学热力学院重点实验室的研究人员在旋转分子马达的分子仿生组装方面取得新进展,研究工作发表在近期出版的Adv Mater（2008,20：601．5）上。细胞生长代谢的整个过程需要能量,绝大多数情况下能量由ATP的高能键水解而获得,而ATP又是通过ATP合酶合成所得到。ATP合酶是线粒体、叶绿体和细菌中能量转化的核心酶,在跨膜质子动力势的推动下催化合成ATP。     

ATP合酶的结构与催化机理

ATP合酶 (F1Fo 复合物) 是生物体内进行氧化磷酸化和光合磷酸化的关键酶.随着核磁共振、X射线晶体衍射、遗传学、化学交联等技术在ATP合酶研究中的广泛应用,ATP合酶的整体结构及其各组成亚基结构的研究都有很大的进展.其中细菌ATP合酶结构的研究更为深入.目前对质子通过Fo的转运方式提出两种模型:单通道和双半通道模型.对扭力矩的形成以及旋转催化也有了进一步的认识.Boyer提出的结合改变机理推动了ATP合酶催化机制的研究,现在主要有两点催化机制和三点催化机制.ATP合酶的催化反应受酶的构象变化和外在条件的调节.     

ATP合酶旋转催化的一种新机制

ATP合酶利用跨膜离子(主要是质子)梯度提供的能量,催化由ADP和Pi(磷酸)合成ATP的反应.已有证据表明,这种催化反应通过ATP合酶内部亚基之间的相对旋转而实现.然而,现有的基于整合在细胞膜内的c环及附着于其上的中心杆(由?和?亚基组成)转动的ATP合酶旋转模型存在多方面的理论缺陷,也与某些实验数据不符.本文提出了一种新的ATP合酶旋转催化模型,其中发生旋转的是?3?3六聚体.具体而言,质子的跨膜转运引起c环的周期性构象改变,从而使得附着在c环上的中心杆产生往复运动,这种往复运动驱动?3?3六聚体的连续转动.这种工作模式与按压式伸缩圆珠笔中推杆的往复运动驱动凸轮产生连续转动的工作机理十分相似.新模型不仅避免了现有模型的理论缺陷,而且更好地解释了已有实验数据.     

生物体内的纳米机器——分子马达

分子马达是生物体内具有马达功能的一类蛋白质大分子纳米机器,可以执行完成生命体内的一切活动,包括肌肉的收缩、细胞内部物质的运输、遗传物质(DNA)的复制、细胞的分裂等等。按照分子马达的不同种类,介绍了各类线性分子马达(如驱动蛋白、动力蛋白和肌球蛋白)的结构、运动方式、主要功能等生物特征,并介绍了旋转分子马达(如ATP合酶)的生物特征,最后进行总结,展望未来。     

高等植物叶绿体ATP合酶ε亚基的结构与功能

ε亚基是叶绿体ATP合酶最小的一个亚基,有阻塞ATP合酶的质子通道和抑制其水解ATP活力的两种功能.用定点突变和缺失等分子生物学方法对ε亚基的结构功能进行了研究,结果表明:ε亚基42位上的苏氨酸(Thr42)对维持其结构和功能都很重要.与大肠杆菌ATP合酶相比,叶绿体ATP合酶ε亚基C端和N端的氨基酸残基缺失对其结构功能的影响更为敏感.     

高等植物叶绿体ATP合酶ε亚基的结构与功能

ε亚基是叶绿体ATP合酶最小的一个亚基,有阻塞ATP合酶的质子通道和抑制其水解ATP活力的两种功能。用定点突变和缺失等分子生物学方法对ε亚基的结构功能进行了研究,结果表明：ε亚基42位上的苏氨酸(Thr42)对维持其结构和功能都很重要。与大肠杆菌ATP合酶相比,叶绿体ATP合酶ε亚基C端和N端的氨基酸残基缺失对其结构功能的影响更为敏感。     

植物细胞中膜H^＋—ATPase的研究进展

本文介绍了植物细胞中各种膜微囊的制备和分离原理,及其在膜转运分子机制研究中的应用。对质膜、线粒体和液泡,膜三种类型膜转运质子ATP酶(H~ -ATPase)的性质进行了比较,说明它们的催化特性和泵质子功能。     

植物细胞中膜H+-ATPase的研究进展

本文介绍了植物细胞中各种膜微囊的制备和分离原理,及其在膜转运分子机制研究中的应用。对质膜、线粒体和液泡,膜三种类型膜转运质子ATP酶(H⁺-ATPase)的性质进行了比较,说明它们的催化特性和泵质子功能。     

F—1ATP酶的三维结构

ATP（三磷酸腺苷）是细胞的化学合成、交换和运动必不可少的动力。这一重要事实人们已经知道了将近50个年头。近20年来,对产生ATP的ATP合成酶在线粒体、叶绿体和细菌的“能量转换”中的重要地位,又得到进一步确认。80年代,Boyer等人首次提出了ATP合成酶催化部分的模型。指出ATP合成酶的催化部分是一个球状体,其中包括a一和卜两类亚基蛋白质,各有3个,相间排列,象陀螺一样旋转。其中卜亚基能催化产生ATP,每旋转一周,3个卜亚基就改变了形状,各自处于不同的状态,分别进行捕捉ATP一前体,催化反应和释放新形成的分子。令人遗…     

分子马达不等间距四态跃迁模型

用主方程方法研究分子马达一维周期性四态不等间距随机跃迁模型,得出稳态情况下分子马达的漂移速度V、扩散系数D及随机参数r,将三者随ATP的浓度［ATP］及外力F的变化进行了曲线拟合,并同大量实验结果进行了比较,定性半定量地分析了分子马达在拖动负载运动时的动力学行为.     

Recent advances in the study of Kaposi's sarcoma-associated herpesvirus replication and pathogenesis

It has now been over twenty years since a novel herpesviral genome was identified in Kaposi's sarcoma biopsies. Since then, the cumulative research effort by molecular biologists, virologists, clinicians, and epidemiologists alike has led to the extensive characterization of this tumor virus, Kaposi's sarcoma-associated herpesvirus(KSHV; also known as human herpesvirus 8(HHV-8)), and its associated diseases. Here we review the current knowledge of KSHV biology and pathogenesis, with a particular emphasis on new and exciting advances in the field of epigenetics. We also discuss the development and practicality of various cell culture and animal model systems to study KSHV replication and pathogenesis.     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

The structure, reproduction and taxonomy of Vidalia and Osmundaria (Rhodophyta, Rhodomelaceae)

Comprises species occurring mostly in subtidal habitats in tropical, subtropical and warm-temperate areas of the world. An analysis of the type species, V. spiralis (Sonder) Lamouroux ex J. Agardh, a species from Australia, establishes basic characters for distinguishing species in the genus. These characters are (1) branching patterns of thalli, (2) flat blades that may be spiralled on their axis, (3) width of the blade, (4) primary or secondary derivation of sterile and fertile branchlets and (5) position of sterile and fertile branchlets on the thalli. Application of the latter two characters provides an important basic method for separation of species into three major groups. Osmundaria , a genus known only in southern Australia, was studied in relation to Vidalia , and its separation from the Vidalia assemblage is not accepted. Species of Vidalia therefore are transferred to the older genus name, Osmundaria. Two new species, Osmundaria papenfussii and Osmundaria oliveae are described from Natal. Confusion in the usage of the epithet, Vidalia fimbriala Brown ex Turner has been clarified, and Vidalia gregaria Falkenberg, described as an epiphyte on Osmundaria pro/ifera Lamouroux, is revealed to be young branches of the host, Osmundaria prolifera.     

New or rare chromosome counts in Artemisia L. (Asteraceae, Anthemideae) and related genera from Kazakhstan

Fifteen chromosome counts of six Artemisia taxa and one species of each of the genera Brachanthemum, Hippolytia, Kaschgaria, Lepidolopsis and Turaniphytum are reported from Kazakhstan. Three of them are new reports, two are not consistent with previous counts and the remainder are confirmations of very scarce (one to four) earlier records. All the populations studied have the same basic chromosome number, x = 9, with ploidy levels ranging from 2x to 6x. Some correlations between ploidy level, morphological characters and distribution are noted.