被子植物雌雄配子及其表膜特异蛋白研究进展

近年来．被子植物雌雄配子的细胞学与生物化学研究取得了一系列重要进展．包括精卵细胞分离纯化、活力保持与检测技术的建立、形态的构观察、生化特性分析及人工体外融合成功，等等．这些进展为创建体外受精操作系统及探讨受精识别机理提供了可能性．被子植物双受精过程存在多位点识别．有关配子水平识别的研究刚刚起步，主要是通过不同途径寻找雌雄配子表膜特异蛋白．其中质膜的纯度与数量问题亟待解决．     

An interspecies conserved antigen ofPlasmodium falciparum containing clusters of asparagine residues

An interspecies conservedPlasmodium asparagine rich antigen, designated as ARK26, was isolated by immunoscreeningP. falciparum genomic DNA expression library with mouse convalescent anti-P. yeolii serum. Partial DNA sequence analysis reveals that ARK26 contains clusters of asparagines and no randomly repeated amino acid sequence motifs are observed. A 65×10³ GST fusion protein is expressed by recombinant plasmid PGEX-5X-1 (ARK26) inE. coli C strain ABLE-K. Computer programs predict that two asparagine rich regions are among the possible antigenic epitopes of p37 encoded by ARK26. Interestingly, the sequence of ARK26 displays significant similarity to yeast and several other species’ mitochondrial genes, and its possible function is discussed. Supported by a fellowship offered by International Center for Genetic Engineering & Biotechnology(ICGEB) Ma Donghui: born in 1969, Graduate student     

Involvement of heterotrimeric G protein in signal transduction of extracellular calmodulin in regulatingrbcS expression

The role of heterotrimeric G protein in signal transduction pathway of extracellular calmodulin in regulating rbcS expression was examined in suspension-cultured cells of transgenic tobacco. Pharmalogical experiments indicated that G protein agonist cholera toxin enhanced rbcS expression and heterotrimeric G protein antagonist pertussis toxin inhibited rbcS expression in transgenic tobacco cells. Pertussis toxin also inhibited the enhancement effect caused by exogenous purified calmodulin on rbcS expression, whereas cholera toxin completely reversed the inhibitory effects caused by anti-calmodulin serum on rbcS expression. The right side-out vesicles from tobacco cell membrane were purified, which contained all of substrates for fluometric assay of GTPase activity. Exogenous purified calmodulin, when adding directly to the medium of plasma membrane vesicles, significantly activated GTPase activity in the right side-out plasma membrane vesicles, and this increase in GTPase activity was completely inhibited both by heterotrimeric G proteins antagonist pertussis toxin and nonhy-drolyzable GTP analogs GMP-PCP. These results provided the evidence that heterotrimeric G proteins may be involved in signal transduction pathways of extracellular calmodulin to regulate rbcS gene expression.     

Rayleigh light scattering and its applications to biochemical analysis

The recent applications of light scattering technique in biochemical analysis have been reviewed. The mechanic theories of resonance light scattering and Rayleigh light scattering (RLS), the relationships and differences between them, their applications and the interference factors in biochemistry analysis have been covered. By contrasting Rayleigh light scattering with double scattering and anti-scattering, the advantages of RLS have been pointed out. Finally, some prospects for the future application of this technique have been given.     

一个新C2H2型锌指蛋白的功能的初步研究

通过筛选人18周胎脑cDNA文库,得到一条编码332AA的全长新基因,生物信息学研究表明,该蛋白质序列有2个C2H2型锌指结构,其中1个锌指结构有RNA－binding蛋白特异锌指的特征,虽然同源比较发现与多种蛋白质精氨酸N端转甲基酶（protein arginine N-methyltransferase) 有一定的同源性,但新锌指蛋白不含转甲基酶的活性功能区域,属功能未知的基因,利用芯片研究功能未知基因的表达是一种较好的手段,通过代谢增强剂PMA（phorbol myristae acetate)刺激培养的血管内皮细胞,观察细胞受激活后新锌指蛋白基因的表达变化,结果表明新基因表达量提高了11倍以上,证实新基因属内皮细胞的极早期应答基因（Immediate early response gene,ERG)。     

美国山核桃不定根形成过程中相关蛋白质 的鉴定及功能分析

美国山核桃是扦插后极难生根的树种,为研究其不定根生根机制,利用MALDI-TOF-MS技术对美国山核桃不定根发育关键时期的差异蛋白进行鉴定分析,发现了48个表达相对差异的蛋白点,选择其中18个差异蛋白进行肽质谱指纹分析并进行同源性比较。结果表明,美国山核桃不定根形成的生理过程中产生了差异蛋白质,其中包括了能量代谢相关蛋白、逆境胁迫相关蛋白和信号传递相关蛋白等差异蛋白。分析可知:能量代谢相关蛋白有ATP合成相关酶类、光合作用相关蛋白及烯醇化酶等; 逆境胁迫相关蛋白与热激蛋白同源; 信号传递相关蛋白主要为细胞色素酶类和血红结合蛋白。     

分形在蛋白质结构分析中的应用

通过介绍分形原理和方法在蛋白质分子结构分析中的应用,表明用分形的方法不仅可以对蛋白质分子结构的复杂性给予定量地描述,而且为人们进一步认识蛋白质的性质和特征提供一些有益的启示和新的信息。     

Increased assembly of cytoskeletal proteins associated with the transformation of human liver cells into fibroblast-like cells

A topoisomerase II inhibitor, novobiocin, and a deacetylase inhibitor, butyrate, synergistically transformed human liver cells into fibroblast-like cells. This morphological change was associated with an increased production of procollagen type III peptide and a simultaneous assembly of actin, tubulin, vimentin and cytokeratin. Novobiocin and butyrate had no marked effect on the phosphorylation state of cytokeratin proteins, but synergistically enhanced [³H]acetate uptake. From these results, it can be speculated that protein acetylation plays an important role in inducing the assembly of cytoskeletal proteins and the morphological transformation of human liver cells.     

Telomeres and chromosomal instability

Telomeres are distinctive structures, composed of a repetitive DNA sequence and associated proteins, which enable cells to distinguish chromosome ends from DNA double-strand breaks. Telomere alterations, caused by replication-mediated shortening, direct damage or defective telomere-associated proteins, usually generate chromosomal instability, which is observed in senescence and during the immortalization process. In cancer cells, this chromosome instability could be extended by their ability to repair chromosomes and terminate in break-fusion-bridge cycles. Dysfunctional telomeres can be healed by activation of telomerase or by the alternative mechanism of telomere lengthening. Activation of such telomere maintenance mechanisms may help to preserve the integrity of chromosomes even if they play a role in chromosomal instability. This review focuses on molecular processes involved in telomere maintenance and chromosomal instability associated with dysfunctional telomeres in mammalian cells.Received 24 July 2003; received after revision 5 September 2003; accepted 11 September 2003