植物磷胁迫蛋白和铁胁迫蛋白研究进展

综述了近十年来国内外有关研究植物磷胁迫蛋白和铁胁迫蛋白的文献,着重阐述了磷胁迫和铁胁迫条件下的植物蛋白质变化,如新的蛋白和新的多肽的特异产生,以及相关的分子生物学进展。     

植物盐胁迫蛋白

本文概述了植物盐胁迫蛋白(saltstress proteins)的种类、性质、分布和可能的生理意义以及与其他逆境蛋白的联系,并介绍对植物耐盐性分子基础的探索。     

植物水分胁迫诱导蛋白的研究进展

主要介绍了植物水分胁迫诱导蛋白的表达模式、特征、分类、功能及其诱导过程中的信号转导及诱导机制。认为胁迫诱导蛋白的产生是植物对逆境胁迫的一种适应性反应,诱导蛋白从多方面保护植物避免或减少胁迫所造成的伤害。植物通过多种途径感受并转导干旱胁迫信号,诱导也多种基因表达产物,从而尽可能地增强对逆境的抗性。     

植物非生物逆境胁迫相关RING finger蛋白

RING finger蛋白是锌指蛋白类中一个庞大的蛋白家族,已成为拟南芥第三大蛋白家族,在水稻中也发现了488个。最典型的结构特点是序列内包含环指结构域(RING finger domain)。RING finger蛋白主要通过泛素化途径参与到植物细胞的生理生化过程。介绍了植物RING finger蛋白的结构特点和分类,综述它们的亚细胞定位,重点阐述它们在响应干旱胁迫、温度胁迫和盐胁迫等非生物逆境胁迫的调控作用。     

植物响应水分胁迫的主要功能蛋白

植物对水分胁迫的响应蛋白根据其在抗逆机制中的作用不同分为调节蛋白和功能蛋白,本文就植物抵抗和适应水分胁迫的活性氧清除机制、渗透调节机制及膜修饰机制相关的主要功能蛋白作一综述。     

扩展蛋白与植物抗逆性关系研究进展

扩展蛋白是一种细胞壁蛋白,可调节细胞壁的松弛和伸展。目前研究表明,扩展蛋白几乎参与调节植物生长发育的整个进程。扩展蛋白还与植物的多种抗性反应有关,在植物对干旱、高盐以及病虫害等生物胁迫和非生物胁迫响应方面起着重要的调节作用。干旱胁迫下扩展蛋白基因的表达与植物的抗旱性有一定的关系;植物的耐盐性受到扩展蛋白基因表达的影响;淹水促进植物的伸长生长与扩展蛋白的表达密切相关;扩展蛋白调节细胞壁松弛为植物抗病性研究提供了新的思路。     

生长素及其运输蛋白对植物铝胁迫的响应

铝对植物的毒害作用主要表现为抑制根尖生长,而根尖生长与生长素及其运输密切相关,铝可能影响了生长素及其代谢过程,但目前尚不清楚生长素及其运输蛋白如何参与植物应对铝胁迫响应。本文通过分析、总结前人研究,并结合自己的前期研究结果,初步阐述生长素或其运输蛋白对植物铝胁迫的响应,即铝影响生长素代谢的相关基因,干扰根尖生长素运输蛋白在细胞内分布及其囊泡运输,调控生长素的极性运榆,进而抑制根尖生长。另一方面,生长素或其运输蛋白又参与了植物应对铝胁迫过程,这主要体现在参与了植物铝毒信号传递、根系铝内置化过程和减缓铝诱导的氧化胁迫。最后,本文提出了生长素及其运输蛋白对植物铝胁迫响应的可能模型。     

盐胁迫下植物细胞离子稳态重建机制

土壤盐渍化是困扰世界粮食产量的一大难题。在盐胁迫环境中,植物获得耐盐能力的一个重要策略是建立新的离子稳态(ionic homeostasis)。盐胁迫下植物细胞离子稳态依赖于膜转运蛋白(泵、载体和离子通道)。利用蛋白质的生化功能分析和突变体功能互补等方法,目前已克隆和鉴定了许多参与离子稳态重建的膜转运蛋白。综述了盐胁迫下植物细胞离子稳态重建的最新研究进展。     

植物铁蛋白与氧化胁迫应激

植物铁蛋白是植物体重要的铁调节蛋白。许多研究表明植物铁蛋白与氧化胁迫抗性之间具有较强关联。植物铁蛋白不仅能抵御高铁产生的氧化毒性,在很多氧化胁迫及环境胁迫抗性中也发挥作用。对植物铁蛋白在氧化及逆境胁迫中的应激加以综述,为铁蛋白在生物工程领域的应用提供理论依据。     

植物ABC转运蛋白及其在Al胁迫下的功能研究进展

ABC(ATP-Binding Cassette)转运蛋白家族是目前已知最大、功能最广泛的蛋自家族,能利用水解ATP的能量来参与生物体内多种物质的转运,这一基因家族成员在哺乳动物和微生物中已广泛鉴定,在植物中的研究是一个相对较新的研究领域.铝是酸性土壤作物生产的一个主要的限制因素,ABC转运蛋白在植物铝耐受性方面有重要作用.该文主要对ABC转运蛋白的特点、生物学功能及植物ABC转运蛋白在Al胁迫下的作用进行了综述,并分析其存在的问题,展望今后可能开展的研究方向.     

二硫键异构酶

天然二硫键的形成是许多蛋白正确折叠中的限速步骤,在稳定蛋白质构象和保持蛋白质活性方面起重要作用。讨论的二硫键异构酶是内质网中一种重要的蛋白折叠催化剂,它催化蛋白二硫键的形成和错误配对二硫键的重排,并有抑制错误折叠蛋白聚集的分子伴侣活性。PDI广泛应用于基因工程上提高外源蛋白表达水平。     

蛋白质二级结构指定

蛋白质二级结构是指蛋白质骨架结构中有规律重复的构象。由蛋白质原子坐标正确地指定蛋白质二级结构是分析蛋白质结构与功能的基础,二级结构的指定对于蛋白质分类、蛋白质功能模体的发现以及理解蛋白质折叠机制有着重要的作用。并且蛋白质二级结构信息广泛应用到蛋白质分子可视化、蛋白质比对以及蛋白质结构预测中。目前有超过20种蛋白质二级结构指定方法,这些方法大体可以分为两大类:基于氢键和基于几何,不同方法指定结果之间的差异较大。由于尚没有蛋白质二级结构指定方法的综述文献,因此,本文主要介绍和总结已有蛋白质二级结构指定方法。     

Effect of Bioregulator Isatin on Protein–Protein Interactions Involving Isatin-Binding Proteins

Isatin (2,3-dioxoindol) is an endogenous low-molecular-weight nonpeptide compound with a wide spectrum of biological and pharmacological activities. It is assumed that isatin acts through isatin-binding proteins. To date, more than a hundred of these proteins are known. Having a different structure and cellular and subcellular localization, they belong to different functional groups. Using the surface plasmon resonance technology, we found earlier that isatin affected the profile of intracellular amyloid-binding proteins and changed the stability of protein complexes in the model system. In fact, this indicates the selective effect of isatin on certain protein–protein interactions (PPI) that occur primarily with the participation of isatinbinding proteins. Therefore, we had formulated the hypothesis that isatin could be a regulator of a protein interactome. This study focuses on the verification of this assumption. Size-exclusion chromatography (SEC) profile of the rat liver tissue lysate along with mass-spectrometric protein identification has revealed 20 isatinbinding proteins that participate in the formation of the protein interactome. About 65 and 25% of them are involved in the formation of multimeric protein complexes and homo/heterodimers, respectively, and only 10% are detected as single molecules. The addition of isatin had a multidirectional effect on the profile of about half of the identified isatin-binding proteins. In some cases, the formation of protein complexes was induced, while in other cases the protein complexes were dissociated. This result confirms the hypothesis of the regulatory effect of isatin on certain PPIs. The data of this work in combination with our previous results allowed us to formulate an “interactomics image” of isatin as a bioregulator, which selectively controls both the formation and dissociation of a number of protein complexes. Two new isatin-dependent proteins were found in the work. This indicates that not all potential target proteins of the regulatory effect of isatin had been previously detected. The study of the molecular mechanisms of isatin action on PPI remains a difficult but priority task for future research.     

Protein phosphorylation in microorganisms

The covalent modification of proteins by phosphorylation constitutes a major regulatory mechanism. It was first recognized in mammalian tissues. A conclusive evidence for the occurrence of protein phosphorylation and protein kinases in coliform bacteria was obtained in 1978. Several phosphate labeled proteins were found when Salmonella typhimurium was pulse-labeled with 32p(i) and solubilized bacterial contents were analyzed by SDS-polyacrylamide gel electrophoresis. In streptomycetes protein phosphorylation has not yet been demonstrated. We found that Streptomyces albus possesses a protein kinase activity. This in vitro protein phosphorylation is cAMP-independent.     

Protein composition of rat bile

In order to characterize the protein composition of rat bile, the bile duct was cannulated in 250 g male Wistar rats and biliary proteins were examined over 48 h. Total protein secretion was monitored by the Cu2+--Folin differential test while individual proteins were characterized by sodium dodecyl sulfate (SDS) and non-SDS polyacrylamide gel electrophoresis. The relative contribution of various proteins was evaluated by densitometric scanning of the stained gels. It was observed that both total biliary protein secretion and the protein polypeptide profiles remained constant throughout the 48h. This is in comparison with biliary bile-acid secretion which fluctuates markedly during this time period both in quantity and composition. It is concluded that biliary secretion is probably not related to the biliary secretion of bile acids.     

Protein kinase C binding partners

Members of the protein kinase C family respond to second messengers and are involved in controlling a broad array of cellular functions. The overlapping specificity and promiscuity of these proteins has promoted the view that specific binding proteins constrain individual family members to create the appropriate specificity of action. It is speculated that such protein kinase C-regulator protein interactions affect substrate availability as well as exposure to allosteric activator(s) and that consequent interactions specify cellular location and impose integration with other signaling systems. These predicted features have been realized in the identification of many protein kinase C interacting proteins and examples of these are discussed.     

ATPase Activity of Latrotoxin-Like Protein

We investigated the ability of latrotoxin-like protein for ATP hydrolysis. It was shown that latrotoxin-like protein possesses ATPase activity, which increases with shift of pH toward alkaline values. A comparison of the enzymatic activity of latrotoxin-like protein at different pH values showed that the kinetic parameters of ATP hydrolysis depend on pH of the incubation medium. It is suggested that the characteristics of latrotoxin-like protein are similar to those of proteins from the AAA-ATPase family, which mediate fusion of cell membranes.     

Location of Sulfate-binding Protein in Salmonella typhimurium

A method is described for location of proteins in bacteria. It depends upon two techniques. One technique is the inactivation of the protein by a reagent which is incapable of penetrating the bacterial membrane (permeability barrier). Proteins inside this membrane cannot be inactivated unless the cells are disrupted; proteins on or outside the membrane can be inactivated. The second technique depends upon inactivation of the protein by specific antibody. Antibody should not penetrate the external bacterial wall, and therefore should only inactivate proteins that are on the wall surface. Thus, proteins can be localized inside the membrane, in the wall-membrane area, or outside the wall. One reagent developed for use with the first technique is diazo-7-amino-1,3-naphthalene-disulfonate. It inactivated beta-galactoside transport, but not beta-galactosidase of intact Escherichia coli. Similarly, it inactivated sulfate binding and transport but not uridine phosphorylase activity of Salmonella typhimurium. This indicates that the sulfate-binding protein is on or outside the cell membrane, and that uridine phosphorylase is inside the cell. The organic mercurial compounds used also showed that the sensitive parts of the sulfate and alpha-methylglucoside transport systems are less reactive than the sensitive part of the beta-galactoside system. Antibody to the sulfate-binding protein inactivated the purified protein but did not inactivate this protein when intact bacteria were employed. Thus, it appears that the sulfate-binding protein does not protrude outside the cell wall. The conclusion that the binding protein is located in the wall-membrane region is supported by its release upon spheroplast formation or osmotic shock, and also by its ability to combine with sulfate in bacteria which cannot transport sulfate into the cell.     

Chirality and Handedness of Protein Structures

In proteins, the polypeptide chain forms a number of right-and left-handed helices and superhelices, right-and left-turned hairpins, and some other structures that are nonsuperimposable, although they are not mirror images of each other as the Lamino acids are not converted to the Damino acids. This property of protein structures will be referred to here as pseudo-chirality–or handedness. It has been shown that there are two kinds of handedness in proteins–helical handedness and handedness of arrangement. Some protein structures exhibit both the kinds of handedness. Handedness is observed at all levels of protein structural organization–from α-helices, β-strands, hairpins, βαβ-units up to complex structural motifs, superhelices, and supramolecular structures in fibrous and polymer proteins. There are several structures that have unique handedness in proteins, for example, α-helices, αα-corners, βαβ-units, abcd-units, and so on. This property of the polypeptide chain is of particular value in protein folding and protein modeling, because it drastically reduces the number of possible folds.