The lectin nature of α-galactosidases from Vicia faba seeds

α-Galactosidase from Vicia faba seeds has been resolved into three molecular forms, I, II¹ and II², respectively. Enzyme I is a tetramer (M_r 160 000) consisting of identical sub-units (M_r 44000 ± 2000). All three forms display lectin activity with glucose/mannose specificity. Enzyme I has been further studied with respect to its lectin specificity and various factors affecting this property. The results indicate that the catalytic and the lectin sites reside in the same protein molecule. The results presented are unique in that the enzyme activity is specific for galactose and its lectin activity is specific for glucose/mannose.     

Plasmon-Assisted Crystalline Silicon Solar Cell with TiO2 as Anti-Reflective Coating

Plasmonics - The present study focuses on the employment of TiO2 (titanium dioxide) film as an anti-reflective coating (ARC) on thin crystalline silicon (Si)-based solar cells along with the...     

Novel insights into the dynamics behavior of glucagon-like peptide-1 receptor with its small molecule agonists

Abstract

The glucagon-like peptide-1 receptor (GLP-1R) is a well-known target of therapeutics industries for the treatment of various metabolic diseases like type 2 diabetes and obesity. The structural–functional relationships of small molecule agonists and GLP-1R are yet to be understood. Therefore, an attempt was made on structurally known GLP-1R agonists (Compound 1, Compound 2, Compound A, Compound B, and (S)-8) to study their interaction with the extracellular domain of GLP-1R. In this study, we explored the dynamics, intrinsic stability, and binding mechanisms of these molecules through computational modeling, docking, molecular dynamics (MD) simulations and molecular mechanics Poisson–Boltzmann surface area (MM/PBSA) binding free energy estimation. Molecular docking study depicted that hydrophobic interaction (pi–pi stacking) plays a crucial role in maintaining the stability of the complex, which was also supported by intermolecular analysis from MD simulation study. Principal component analysis suggested that the terminal ends along with the turns/loops connecting adjacent helix and strands exhibit a comparatively higher movement of main chain atoms in most of the complexes. MM/PBSA binding free energy study revealed that non-polar solvation (van der Waals and electrostatic) energy subsidizes significantly to the total binding energy, and the polar solvation energy opposes the binding agonists to GLP-1R. Overall, we provide structural features information about GLP-1R complexes that would be conducive for the discovery of new GLP-1R agonists in the future for the treatment of various metabolic diseases.

Communicated by Ramaswamy H. Sarma     

The carboxy-terminus,a key regulator of protein function

All proteins end with a carboxyl terminus that has unique biophysical properties and is often disordered. Although there are examples of important C-termini functions, a more global role for the C-terminus is not yet established. In this review, we summarize research on C-termini, a unique region in proteins that cells exploit. Alternative splicing and proteolysis increase the diversity of proteins and peptides in cells with unique C-termini. The C-termini of proteins contain minimotifs, short peptides with an encoded function generally characterized as binding, posttranslational modifications, and trafficking. Many of these activities are specific to minimotifs on the C-terminus. Approximately 13% of C-termini in the human proteome have a known minimotif, and the majority, if not all of the remaining termini have conserved motifs inferring a function that remains to be discovered. C-termini, their predictions, and their functions are collated in the C-terminome, Proteus, and Terminus Oriented Protein Function INferred Database (TopFIND) database/web systems. Many C-termini are well conserved, and some have a known role in health and disease. We envision that this summary of C-termini will guide future investigation of their biochemical and physiological significance.     

A single-step chromatographic method for the purification of proteins devoid of exposed histidine residues

The principle of the immobilized metal affinity chromatography (IMAC) is based on the differences in the affinity of proteins for metal ions bound in a 1:1 complex of iminodiacetic acid (IDA) immobilized on a chromatographic support. A single step purification was carried out for luteinizing hormone (LH) on Cu2+, Zn2+, Ni2+, and Co2+ IDA Sepharose affinity columns. Highly purified LH was obtained with a Cu2+ IDA Sepharose column. SDS-PAGE and Western blot analysis were done to confirm the purity of the hormone. Biological activity has been evaluated by radio-immunoassay. This method was found economically viable and suitable for the recovery of biologically active hormone.     

Visualization and quantification of <Emphasis Type="Italic">Plasmodium falciparum</Emphasis> intraerythrocytic merozoites

Malaria, a leading parasitic killer, is caused by Plasmodium spp. The pathology of the disease starts when Plasmodium merozoites infect erythrocytes to form rings, that matures through a large trophozoite form and develop into schizonts containing multiple merozoites. The number of intra-erythrocytic merozoites is a key-determining factor for multiplication rate of the parasite. Counting of intraerythrocytic merozoites by classical 2-D microscopy method is error prone due to insufficient representation of merozoite in one optical plane of a schizont. Here, we report an alternative 3-D microscopy based automated method for counting of intraerythrocytic merozoites in entire volume of schizont. This method offers a considerable amount of advantages in terms of both, ease and accuracy.     

X-ray analysis of Mycobacterium smegmatis Dps and a comparative study involving other Dps and Dps-like molecules

The structure of the DNA binding protein from starved cells from Mycobacterium smegmatis has been determined in three crystal forms and has been compared with those of similar proteins from other sources. The dodecameric molecule can be described as a distorted icosahedron. The interfaces among subunits are such that the dodecameric molecule appears to have been made up of stable trimers. The situation is similar in the proteins from Escherichia coli and Agrobacterium tumefaciens, which are closer to the M.smegmatis protein in sequence and structure than those from other sources, which appear to form a dimer first. Trimerisation is aided in the three proteins by the additional N-terminal stretches that they possess. The M.smegmatis protein has an additional C-terminal stretch compared to other related proteins. The stretch, known to be involved in DNA binding, is situated on the surface of the molecule. A comparison of the available structures permits a delineation of the rigid and flexible regions in the molecule. The subunit interfaces around the molecular dyads, where the ferroxidation centres are located, are relatively rigid. Regions in the vicinity of the acidic holes centred around molecular 3-fold axes, are relatively flexible. So are the DNA binding regions. The crystal structures of the protein from M.smegmatis confirm that DNA molecules can occupy spaces within the crystal without disturbing the arrangement of the protein molecules. However, contrary to earlier suggestions, the spaces do not need to be between layers of protein molecules. The cubic form provides an arrangement in which grooves, which could hold DNA molecules, criss-cross the crystal.     

Role of proteins in resistance mechanism of Pseudomonas fluorescens against heavy metal induced stress with proteomics approach

The genus Pseudomonas is a group of gram-negative, motile, rod-shaped bacteria known for their metabolic versatility. One of the species is Pseudomonas fluorescens, which has an efficient system for detoxification of industrial waste. Other aspects include, catabolic versatility, excellent root colonizing abilities and capacity to produce a wide range of antifungal metabolites. They are also known for their resistance and survival in the presence of several organic and inorganic pollutants. P. fluorescens has also been isolated from metal polluted water and soils but the elucidation of proteins responsible for its survival is still not clear. The aim of the study was to elucidate the differential protein expression of this bacterium when exposed to heavy metal stress, using two-dimensional electrophoresis. The proteins spo VG and enolase showed upregulation during the bacterial exposure to lead and copper. Hypothetical protein showed downregulation when bacterium was exposed to cobalt. Some proteins like xylosyltransferase, ORF 18 phage phi KZ, OMP H1 and translational elongation factor EF-Tu appeared only during their exposure to cobalt. These were absent in the control condition. Analysis of the differentially expressed proteins as well as the newly synthesized proteins along with the results obtained growth and enzyme activity indicate the involvement of all these factors in the survival of this organism in the presence of heavy metals.