细菌中D-氨基酸生物合成及调控作用研究进展

细菌中普遍存在L/D型氨基酸,与L-氨基酸(L-AAs)不同,D-氨基酸(D-AAs)不参与蛋白质合成,而与细胞壁肽聚糖的合成有关,直接影响细菌细胞壁的形状、数量和强度。D-AAs在细菌表征、药物抑菌性、靶标确定等方面具有重要的作用。目前,外源添加D-AAs参与肽聚糖合成的机制已有一些研究进展,其荧光衍生物已应用于细菌可视化,特异性探测细胞壁形成/重塑、细菌生长和细胞形态。但D-AAs如何影响细菌生长及其抗逆性的机制尚未研究清楚。对D-AAs的研究现状进行综述,重点介绍D-AAs在细菌中的生物合成机制和参与细胞壁合成的机制、非典型DAAs对细菌的调控以及在细菌可视化中的应用,并对D-AAs未来研究方向进行了展望。     

肽聚糖的生物合成及其调控机制研究进展

肽聚糖(peptidoglycan)是细菌细胞壁的重要组成部分,对于维持细胞形态、大小及存活至关重要;同时,肽聚糖是众多常用抗生素的作用靶点。在细菌的正常生长过程中,肽聚糖不断地合成和水解,为了保证细胞壁的完整性,肽聚糖生物合成过程必然受到严谨的时空调控。肽聚糖的生物合成及其调控机制是微生物学中重要的基础研究之一,近年来国内外研究团队在该领域取得了突破性研究进展。基于此,本文综述了肽聚糖的从头合成和循环再利用过程,并重点阐述了肽聚糖合成关键酶——肽聚糖合酶及其调控机制的最新研究进展。最后,本文对未来需要加强研究的方向进行了展望。     

非蛋白氨基酸的生物合成及其生物学作用

解释了蛋白氨基酸和非蛋白氨基酸,并着重论述了非蛋白氨基酸的生物合成及其生物学作用。非蛋白氨基酸的生物合成主要通过基本氨基酸合成后的修饰、代谢及消旋作用产生,其生物学作用主要表现在能合成其他含氮物质、储藏氮和运输氮、储能、组成细菌细胞壁、毒性作用及药物作用等方面。     

青霉素结合蛋白及其介导细菌耐药的研究进展

青霉素结合蛋白(PBPs)是一类广泛存在于细菌细胞膜表面的膜蛋白,是β-内酰胺类抗生素的主要作用靶位。在细菌合成细胞壁肽聚糖的过程中,PBPs主要发挥糖基转移酶、肽基转移酶和D-丙氨酰-D-丙氨酸羧肽酶(D,D-羧肽酶)活性,是细菌生长繁殖中不可或缺的酶。不同种类细菌所含PBPs各不相同,其结构的改变、数量的增多、与抗生素亲和力的下降以及产生新的青霉素结合蛋白是直接导致细菌对β-内酰胺类抗生素产生耐药性的重要原因。随着各类抗菌药物在临床上的广泛应用,细菌对抗菌药物的耐药问题日趋严重,其耐药水平也越来越高。因此,近年来全球围绕PBPs开展的研究工作越来越多。本文对PBPs的分类、结构和功能、与细菌耐药性的关系及检测方法的最新研究进展进行综述,并对未来可能的研究方向进行展望。     

Expansin(细胞壁松弛蛋白)的发展

Expansin是一种体外诱导分离的植物细胞壁伸展的蛋白,在修饰细胞壁基础上使细胞膨胀。Expansin的功能众多,除了促进细胞生长,还包括影响营养生长、形态发生、授粉受精、果实软化等,并表现出高度的组织、器官和细胞特异性。目前已经在多种植物及其他一些生物范围内对expansin及类expansin序列和蛋白质进行了研究,并对它们的作用机制进行了探索。     

金黄色葡萄球菌壁磷壁酸致病与免疫的分子机制研究进展

金黄色葡萄球菌(Staphylococcus aureus)壁磷壁酸(wall teichoic acids, WTAs)是多元醇经由磷酸二酯键共价连接组成的细胞壁表面阴离子糖类聚合物,参与调节细胞壁的稳态并介导细菌毒力。金黄色葡萄球菌WTAs与宿主细胞表面特定的受体结合,可诱导天然免疫和获得性免疫应答。此外,金黄色葡萄球菌WTAs还参与调控毒力基因的表达,有助于细菌的定殖感染,在基因工程靶标治疗和噬菌体药物治疗方面具有广泛的应用前景。本文对金黄色葡萄球菌WTAs的合成进行了概述,综述了WTAs对宿主免疫应答的调控作用,以及在细菌对宿主侵袭与定殖中的致病机制,并归纳WTAs的耐药分子机制和作为药物治疗靶标的研究现状。这些研究为揭示WTAs的致病与免疫分子机制提供研究思路,为预防和治疗金黄色葡萄球菌的感染提供新的策略。     

SEDS蛋白的结构与功能研究进展

肽聚糖是细菌细胞壁的主要成分,在维持细胞活性、形状和保护渗透压等方面起着重要作用。SEDS(shape,elongation,division,and sporulation)蛋白是参与肽聚糖合成的一类膜蛋白家族,其成员与细胞形状、伸长、分裂和孢子形成有关。一系列遗传和生化证据表明,SEDS蛋白具有糖基转移酶功能,是细胞延长和分裂机制的核心聚合酶。SEDS蛋白分布的广泛性、结构的保守性和功能的重要性,使其有望成为新一代抗生素研究的重要靶标。该文对SEDS蛋白的结构和功能进行了综述,重点介绍了SEDS蛋白的结构及其参与肽聚糖合成的调控机制,并对SEDS蛋白的应用和前景进行了展望。     

革兰氏阴性细菌β-桶状结构外膜蛋白折叠与组装的研究进展

β-桶状结构外膜蛋白是革兰氏阴性细菌细胞外膜层的主要组成部分,在营养吸收、维持外膜完整性、病原菌致病性及多重耐药性等方面发挥着重要的作用,对细菌的存活至关重要。详细了解这些蛋白的合成、折叠与组装到外膜的过程在增加筛选抗病原菌药物靶位、增强有益菌的生物活性等方面具有重要意义。本文对近年来革兰氏阴性细菌β-桶状结构外膜蛋白的合成、转运、折叠及组装到外膜过程的研究结果进行了综合论述,重点叙述了β-桶状结构外膜蛋白组装复合体的研究进展,并在此基础对这一类蛋白的折叠与膜整合过程提出一些新的见解,便于读者快速、全面了解该领域的最新发现和发展。     

革兰氏阴性细菌β-桶状结构外膜蛋白折叠与组装的研究进展

摘要:β-桶状结构外膜蛋白是革兰氏阴性细菌细胞外膜层的主要组成部分,在营养吸收、维持外膜完整性、病原菌致病性及多重耐药性等方面发挥着重要的作用,对细菌的存活至关重要。详细了解这些蛋白的合成、折叠与组装到外膜的过程在增加筛选抗病原菌药物靶位、增强有益菌的生物活性等方面具有重要意义。本文对近年来革兰氏阴性细菌β-桶状结构外膜蛋白的合成、转运、折叠及组装到外膜过程的研究结果进行了综合论述,重点叙述了β-桶状结构外膜蛋白组装复合体的研究进展,并在此基础对这一类蛋白的折叠与膜整合过程提出一些新的见解,便于读者快速、全面了解该领域的最新发现和发展。     

c-di-AMP——细菌中第二信使的研究进展

环二腺苷酸(cyclic diadenylate monophosphate,c-di-AMP)是新发现的在细菌中广泛存在的一类重要的第二信使。c-di-AMP不仅与细菌的生长、细胞壁的代谢平衡、生物被膜的形成等密切相关,还在真核宿主细胞抗感染的固有免疫中发挥重要作用。主要从c-di-AMP的合成酶与降解酶、c-di-AMP在病原菌中的结合蛋白以及c-di-AMP与宿主细胞互作过程中的相关受体蛋白等几方面进行综述。     

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.