伸展蛋白的结构、功能、交联和生物合成

伸展蛋白是细胞壁中一类富含羟脯氨酸、具有Ser-Hyp-Hyp-(X)-Hyp-Hyp特征性结构单位的糖蛋白。它们不仅是初生壁的重要结构成分,而且在细胞的防御及抗病抗逆性中起作用。伸展蛋白过氧化物酶能在体外将伸展蛋白单体交联成多聚体。酪氨酸残基参与交联并形成异二酪氨酸(IDT)。伸展蛋白的合成和翻译后修饰分别在细胞质和内质网等膜系统中进行。     

共价结合于细胞壁的过氧化物酶与黄瓜子叶细胞扩大生长的关系

植物细胞包括原生质体的生长,都依赖于细胞壁的伸展。而壁结合伸展素又是影响细胞壁伸展最直接的因素,Lamport(1965,1967)报道羟脯氨酸残基通过O-阿拉伯糖苷键与壁中其他多聚体相连,形成网络,调节壁伸展。Fry(1982,1984)分离到一种异联酪氨酸后,认为这是多肽链间的两个酪氨酸经二酚醚键氧化偶联而     

参与植物天然免疫的LRR型蛋白

植物含有多种富含亮氨酸重复序列(LRRs)结构的蛋白质,它们在植物天然免疫中发挥着重要作用。参与植物防御反应的LRR型蛋白家族包括:类受体蛋白激酶、抗病基因编码蛋白质、多聚半乳糖醛酸酶抑制蛋白和伸展蛋白家族。最近,人们发现植物免疫系统包含:病原相关分子模式(PAMP)激发的免疫性(PTI),即类受体蛋白激酶识别病原菌PAMPs,启动植物防卫反应;病原菌效应子激发的免疫性(ETI),即抗病基因编码蛋白质识别效应子,启动植物防卫反应。除此之外,细胞壁是植物细胞的天然保护屏障。多聚半乳糖醛酸酶抑制蛋白和伸展蛋白通过维护细胞壁,抵御病原菌入侵。我们综述了植物中LRRs蛋白的结构特征与不同种类的LRR蛋白介导免疫反应的分子机制,讨论了LRR型蛋白在植物免疫过程中的意义及存在的问题,指出搜寻配体和下游信号分子将是LRR型蛋白研究热点。     

大豆幼苗下胚轴扩张蛋白的存在及其特性

用离体细胞壁伸展活性重组法,对大豆（Ｇｌｙｃｉｎｅｍａｘ（Ｌ．）Ｍｅｒ．）幼苗下胚轴细胞壁特异性扩张蛋白的活性鉴定和特性研究结果表明,大豆幼苗下胚轴的延伸生长,既与扩张蛋白的活性升高有关,也与其细胞壁对扩张蛋白的敏感性增加有关;热钝化大豆下胚轴细胞壁的伸展活性,一旦被外源扩张蛋白所恢复,用酸性缓冲液（ｐＨ４．５）代替扩张蛋白提取液,伸展活性不受影响;但若换用中性缓冲液（ｐＨ６．８）,伸展活性丧失殆尽,且与活细胞壁一样,随缓冲液的交替更换而反复逆转;大豆和黄瓜幼苗扩张蛋白可以与其热钝化的细胞壁相互交叉重组。另外,重组的细胞壁伸展活性对扩张蛋白浓度和ｐＨ的依赖性,符合一般酶的催化特征,说明扩张蛋白不仅在植物细胞的延伸生长过程中起着极为重要的作用,而且还暗示植物细胞壁的内源伸展就是该蛋白介导的一种生物化学过程。     

植物细胞壁研究进展

植物细胞壁是一种复杂的网状结构,其成分包含纤维素、半纤维素、果胶和少量的结构蛋白等。在植物细胞生长过程中,细胞能产生伸展素蛋白,打断纤维素和半纤维素之间的氢键,引起细胞膨压驱动的细胞壁扩张。成熟细胞壁扩张性的丧失是由于细胞壁硬化作用而对扩张性蛋白的作用不敏感造成的,细胞壁成熟过程中很多不同的连接会同时发生,当细胞壁基质多聚体分子之间的连接增加到一定的程度。细胞壁的伸长就会被完全抑制。     

植物伸展蛋白的基因及其表达的调控

植物细胞壁中存在多种伸展蛋白。它们由伸展蛋白多基因族编码。调节伸展蛋白基因表达的因素有遗传密码使用的倾向性、发育程序、机械损伤、乙烯、病原和植物抗毒素诱导剂等。     

植物细胞壁伸展蛋白的功能与利用

伸展蛋白是一类富含羟脯氨酸的糖蛋白,是植物细胞壁中重要的结构蛋白。伸展蛋白家族基因广泛存在于多种植物中,参与植物细胞壁网络结构形成与修饰、植物细胞伸长、根生长发育等过程,并且影响植物机械强度、倒伏抗性和各种逆境胁迫反应。本文拟从蛋白结构、进化关系、生物学功能等方面介绍植物伸展蛋白近期研究进展,并初步提出了此类基因在农作物和能源植物遗传改良中的利用。     

植物伸展蛋白的研究进展

伸展蛋白是高等植物细胞壁中一族富含羟脯氨酸的糖蛋白,在植物细胞壁中发挥着重要的生理功能。综述了近几十年对伸展蛋白结构、功能、基因家族以及生物合成与基因表达调节的研究进展。     

双酚A暴露对哺乳动物精子蛋白酪氨酸磷酸化的影响

双酚A(BPA)是一种人工合成的雌激素性化合物,广泛存在于环境中,对哺乳动物内分泌有干扰作用,影响雄性生殖系统功能。本研究以新鲜猪精子、17 ℃保存猪精子以及小鼠精子为对象,采用体外培养方法,利用蛋白免疫印迹(WB)和免疫荧光技术,分析不同浓度BPA(0、0.1、1、10、100 μmol·L^-1)暴露对哺乳动物精子蛋白酪氨酸磷酸化的影响及分子机制。结果表明: 低中浓度(0.1、1 μmol·L^-1)BPA暴露对新鲜猪获能精子蛋白酪氨酸磷酸化具有显著促进作用,但在高浓度(10、100 μmol·L^-1)BPA暴露下,猪获能精子蛋白酪氨酸磷酸化呈现降低趋势。BPA暴露下,小鼠获能精子蛋白酪氨酸磷酸化随BPA浓度的增加而增强,并且BPA影响猪和小鼠精子获能相关酪氨酸磷酸化修饰的蛋白种类不同。表明BPA暴露对哺乳动物精子的影响具有物种特异性。免疫荧光结果显示BPA对精子蛋白酪氨酸磷酸化的影响主要发生在鞭毛的中段和主段。     

植物细胞壁松弛蛋白——膨胀素

膨胀素(expansin,也称作扩张素或扩张蛋白)是一种引起植物细胞壁松弛的蛋白质,在植物细胞伸展以及一系列涉及细胞壁修饰的生命活动中起着关键作用。膨胀素由多基因家族编码,目前的研究表明膨胀素超家族由4个基因亚家族构成。膨胀素存在于不同的种属植物中,并克隆了大量的扩张蛋白基因。综述了近年来国内外有关膨胀素基因和蛋白的结构特征及作用机制等方面的研究进展。     

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.     

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.     

肝癌中HBV和HCV基因和抗原的分布及意义

采用原位分子杂交方法检测HCV RNA及HBV X基因;采用免疫组织化学方法研究HCV核心抗原,非结构区C33c抗原及HBxAg在肝细胞肝癌中的定位及分布.结果表明(1)HCV RNA、HBV X基因在肝细胞肝癌组织检出率分别为40%(55/136)和82%(112/136).HCV RNA定位于癌细胞的胞浆内,阳性细胞呈散在、灶状及弥漫分布三种形式;HBV X基因在肝癌细胞中的分布呈胞浆型、核型及核浆型,阳性细胞也呈上述三种分布形式;(2)HCV C33c抗原、核心抗原在肝细胞肝癌中的阳性率为81%(133/164)及86%(141/164).C33c抗原定位于癌细胞及肝细胞的胞浆内;核心抗原既定位于癌细胞核中,又可定位于胞浆中.C33c抗原阳性细胞以灶状分布为主;而核心抗原阳性细     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.