Isozymes in macroalgae (seaweeds): genetic differentiation,genetic variability and applications in systematics

Use of isozymes (including allozymes) in studies of population genetics and systematics of seaweeds has increased sufficiently in the last decade to allow some generalization. Only a single locus has been observed for about half the enzymes analysed in seaweeds, compared with 29% in vascular plants. Compared with higher plants, macroalgal species generally have low amounts of electrophoretically detectable genetic variation; the lowest levels of genetic variation found in natural populations are those reported for seaweeds. Nonetheless, seaweeds show an association between levels of genetic diversity as revealed by isozymes and species-specific attributes, such as mating system and predominance of asexual versus sexual reproduction. In systematic studies, isozymes have revealed cryptic species and identified pairs of sibling taxa. The quaternary structure of enzymes appears to be conserved at the phylum level. With the current availability of improved techniques for enzyme electrophoresis and for data interpretation, we expect future studies utilizing isozyme electrophoresis to provide further insight into population and evolutionary processes in seaweeds.     

Techniques and applications of NMR to membrane proteins (Review)

The fact that membrane proteins are notoriously difficult to analyse using standard protocols for atomic-resolution structure determination methods have motivated adaptation of these techniques to membrane protein studies as well as development of new technologies. With this motivation, liquid-state nuclear magnetic resonance (NMR) has recently been used with success for studies of peptides and membrane proteins in detergent micelles, and solid-state NMR has undergone a tremendous evolution towards characterization of membrane proteins in native membrane and oriented phospholipid bilayers. In this mini-review, we describe some of the technological challenges behind these efforts and provide examples on their use in membrane biology.     

Foreword: Protein acylation and microdomains in membrane function

The Signal Recognition Particle (SRP) plays a critical role in the sorting of nascent secretory and membrane proteins. Remarkably, this function has been conserved from bacteria, where SRP delivers proteins to the inner membrane, through to eukaryotes, where SRP is required for targeting of proteins to the endoplasmic reticulum. This review focuses on present understanding of SRP structure and function and the relationship between the two. Furthermore, the similarities and differences in the structure, function and cellular role of SRP in bacteria, chloroplasts, fungi and mammals will be stressed.     

Ion channels of glutamate receptors: structural modeling

Ionotropic glutamate receptors belong to the superfamily of P-loop channels as well as K⁺, Na⁺, and Ca²⁺ channels. However, the structural similarity between ion channels of the glutamate receptors and K⁺ channels is a matter of discussion. The aim of this study was to analyze differences between the structures of K⁺ channels and glutamate receptor channels. For this purpose, homology models of NMDA and AMPA receptor channels (M2 and M3 segments) were built using X-ray structures of K⁺ channels as templates. The models were optimized and used to reproduce specific data on the structure of glutamate receptor channels. Particular attention was paid to the data of the binding of channel blockers and to the results of scanning mutagenesis. The modeling demonstrates that properties of glutamate receptor channel can be reproduced assuming only local structural deformations of the K⁺ channel templates. The most valuable differences were found in the selectivity-filter region, whereas helical parts of M2 and M3 segments could have similar spatial organization with homologous segments in K⁺ channels. It is concluded that the current experimental data on glutamate receptor channels does not reveal global structural differences with K⁺ channels.     

Genetic diversity and population structure of Butea monosperma (Lam.) Taub.- a potential medicinal legume tree

Three molecular marker systems, Random Amplified Polymorphic DNA (RAPD), Inter-Simple Sequence Repeats (ISSR) and Sequence-Related Amplified Polymorphism (SRAP) were employed to investigate the genetic structure and diversity among the 14 natural populations of Butea monosperma collected from different geographical regions of India. Detected by 17 RAPD, 15 ISSR and 11 SRAP primer combinations, the proportions of polymorphic bands were 84.2 %, 77.2 % and 91.9 %, respectively, and the mean Nei’s genetic distances among the populations were 0.13, 0.10 and 0.13, respectively. Partitioning of genetic variability by Analysis of molecular variance (AMOVA) revealed that the high genetic diversity was distributed within the populations. AMOVA also revealed that the coefficient of gene differentiation among populations based on F_ST was very high irrespective of markers used. The overall gene flow among populations (Nm) was very low. Cophenetic correlation coefficients of Nei’s distance values and clustering pattern by Mental test were statistically significant for all three marker systems used but poor fit for ISSR data than for RAPD, SRAP and combined data set of all three markers. For all markers, a high similarity in dendrogram topologies was obtained, although some differences were observed with ISSR. The dendrogram obtained by RAPD, SRAP and combined data set of all three markers reflect relationship of most of the populations according to their geographic distribution.     

Structure modeling and antidiabetic activity of a seed protein of Momordica charantia in non-obese diabetic (NOD) mice

Momordica charantia is a well known medicinal plant used in the traditional medicinal system for the treatment of various diseases including diabetes mellitus. Recently, a novel protein termed as ADMc1 from the seed extract of M. charantia has been identified and isolated showing significant antihyperglycemic activity in type 1 diabetic rats in which diabetes was induced. However, the structure of this protein has not yet been analyzed. Homology modeling approach was used to generate a high quality protein 3D structure for the amino acid sequence of the ADMc1 protein in this study. The comparative assessment of secondary structures revealed ADMc1 as an all-alpha helix protein with random coils. Tertiary structure predicted on the template structure of Napin of B. Napus (PDB ID: 1SM7) with which the ADMc1 showed significant sequence similarity, was validated using protein structure validation tools like PROCHECK, WHAT_CHECK, VERIFY3D and ProSA. Arrangement of disulfide bridges formed by cysteine residues were predicted by the Dianna 1.1 server. The presence of multiple disulfide bond confers the stable nature of the ADMc1 protein. Further, the biological activity of the ADMc1 was assessed in non-obese diabetic (NOD) mice which are spontaneous model of type 1 diabetes. Significant reduction in the blood glucose levels of NOD mice was observed up to 8 h post administration of the rADMc1 protein. Overall, the structural characterizations with antihyperglycemic activity of this seed protein of Momordica charantia demonstrate its potential as an antidiabetic agent.     

植物Rab蛋白的研究进展

Rab蛋白是小G蛋白超级家族中的成员之一。通过Rab蛋白氨基酸序列的系统进化分析表明,植物Rab家族又可分为8个亚家族,分别为RabA、RabB、RabC、RabD、RabE、RabF、RabG和RabH。Rab蛋白一般位于胞内特异膜系统的胞质面,它们是小泡运输的关键调节因子。Rab蛋白有非常保守的结构域,同时又具有功能多样性,它们在细胞分化、顶端优势、花粉管发育、根瘤形成以及生物和非生物胁迫反应中均起着非常重要的作用。该文对近年来国内外有关植物Rab蛋白的结构特点及其多样性功能的研究进展进行综述。     

宁夏10种观赏灌木叶片解剖结构及其抗旱性综合评价

采用显微制片技术,对宁夏10种主要灌木树种叶片的解剖结构进行了观察,分别测定了叶片厚度、上下角质层厚度、栅栏组织、海绵组织、气孔密度等15个与抗旱性相关的指标,并对15个指标进行主成分分析,用隶属函数法对10种灌木的抗旱性进行了综合评价。结果表明:10种灌木的叶片具有典型的旱生结构,大多数具有表皮毛,且具有明显的角质层结构;上、下表皮细胞及叶肉细胞排列紧密。15个指标在各灌木树种间的差异均极显著,其中叶片厚度、上角质层、栅栏组织厚度、气孔密度和主脉维管束直径为叶片旱性结构的主要因子。通过5个主要因子的综合评价,10种灌木的抗旱性大小顺序依次为:沙冬青>花棒>蒙古莸>金叶莸>互叶醉鱼草>蒙古扁桃>鞑靼忍冬>葱皮忍冬>金花忍冬>台尔曼忍冬。