Genetic disruption of mammalian endoplasmic reticulum-associated protein degradation: Human phenotypes and animal and cellular disease models

Endoplasmic reticulum-associated protein degradation (ERAD) is a stringent quality control mechanism through which misfolded, unassembled and some native proteins are targeted for degradation to maintain appropriate cellular and organelle homeostasis. Several in vitro and in vivo ERAD-related studies have provided mechanistic insights into ERAD pathway activation and its consequent events; however, a majority of these have investigated the effect of ERAD substrates and their consequent diseases affecting the degradation process. In this review, we present all reported human single-gene disorders caused by genetic variation in genes that encode ERAD components rather than their substrates. Additionally, after extensive literature survey, we present various genetically manipulated higher cellular and mammalian animal models that lack specific components involved in various stages of the ERAD pathway.     

Highly enhanced adsorption for decontamination of lead ions from battery wastewaters using chitosan functionalized with xanthate

Decontamination of lead ions from aqueous media has been investigated using cross linked xanthated chitosan (CMC) as an adsorbent. Various physico-chemical parameters such as contact time, amount of adsorbent, concentration of adsorbate were optimized to simulate the best conditions which can be used to decontaminate lead from aqueous media using CMC as an adsorbent. The atomic absorption spectrometric technique was used to determine the distribution of lead. Maximum adsorption was observed at both pH 4 and 5. The adsorption data followed both Freundlich and Langmuir isotherms. Langmuir isotherm gave a saturated capacity of 322.6+/-1.2mg/g at pH 4. From the FTIR spectra analysis, it was concluded that xanthate and amino group participate in the adsorption process. The developed procedure was successfully applied for the removal of lead ions from real battery wastewater samples.     

Molecular and computational approaches to understand resistance of New Delhi metallo β-lactamase variants (NDM-1, NDM-4, NDM-5, NDM-6, NDM-7)-producing strains against carbapenems

The discovery of NDM-1 and its variants has caused the emergence of antibiotic resistance in the community and hospital setting, causing major concern for health care across the globe. New Delhi Metallo-β-lactamase is known to hydrolyse almost all β-lactam antibiotics. Studies have shown the hydrolytic activates of NDM-1 and some of its variants, however a comparative study of these NDM variants has not been explored in detail. Hence, we proposed to check their catalytic activity by performing a comparative study between NDM-1 and its variants. The study was initiated to clone NDM variants (NDM-1, NDM-4, NDM-5, NDM-6 and NDM-7) followed by overexpression of the recombinant proteins to check their hydrolytic properties against β-lactam antibiotics. The minimum inhibitory concentration of carbapenems antibiotics for bla_NDM-5 clone was found four fold increased, whereas no change was observed in the clones having other variants. The hydrolytic activity of carbapenem with NDM-5 variant was found to be augmented as per the kinetics parameter where Km was decreased and kcat, kcat/Km values increased as compared to the NDM-1. Molecular docking studies were employed to identify the variations in the binding ability among all NDM variants with imipenem or meropenem. Simulation studies at 100?ns showed a good stability of NDM-5 with imipenem and meropenem as compared to NDM-1. CD spectroscopy data revealed significant changes in the secondary structure of NDM variants. We conclude that NDM-5 showed higher hydrolytic activity as compared to other variants. This study provides a comparative analysis of the severity of NDM producing strains.     

Improving the accuracy of a solid spherical source radius and depth estimation using the diffusion equation in fluorescence reflectance mode

Background  

Non-invasive planar fluorescence reflectance imaging (FRI) is used for accessing physiological and molecular processes in biological tissue. This method is efficiently used to detect superficial fluorescent inclusions. FRI is based on recording the spatial radiance distribution (SRD) at the surface of a sample. SRD provides information for measuring structural parameters of a fluorescent source (such as radius and depth). The aim of this article is to estimate the depth and radius of the source distribution from SRD, measured at the sample surface. For this reason, a theoretical expression for the SRD at the surface of a turbid sample arising from a spherical light source embedded in the sample, was derived using a steady-state solution of the diffusion equation with an appropriate boundary condition.     

Molecular recognition of lipopolysaccharide by the lantibiotic nisin

Nisin is a lanthionine antimicrobial effective against diverse Gram-positive bacteria and is used as a food preservative worldwide. Its action is mediated by pyrophosphate recognition of the bacterial cell wall receptors lipid II and undecaprenyl pyrophosphate. Nisin/receptor complexes disrupt cytoplasmic membranes, inhibit cell wall synthesis and dysregulate bacterial cell division. Gram-negative bacteria are much more tolerant to antimicrobials including nisin. In contrast to Gram-positives, Gram-negative bacteria possess an outer membrane, the major constituent of which is lipopolysaccharide (LPS). This contains surface exposed phosphate and pyrophosphate groups and hence can be targeted by nisin. Here we describe the impact of LPS on membrane stability in response to nisin and the molecular interactions occurring between nisin and membrane-embedded LPS from different Gram-negative bacteria. Dye release from liposomes shows enhanced susceptibility to nisin in the presence of LPS, particularly rough LPS chemotypes that lack an O-antigen whereas LPS from microorganisms sharing similar ecological niches with antimicrobial producers provides only modest enhancement. Increased susceptibility was observed with LPS from pathogenic Klebsiella pneumoniae compared to LPS from enteropathogenic Salmonella enterica and gut commensal Escherichia coli. LPS from Brucella melitensis, an intra-cellular pathogen which is adapted to invade professional and non-professional phagocytes, appears to be refractory to nisin. Molecular complex formation between nisin and LPS was studied by solid state MAS NMR and revealed complex formation between nisin and LPS from most organisms investigated except B. melitensis. LPS/nisin complex formation was confirmed in outer membrane extracts from E. coli.     

The C-Terminus of ClpC1 of Mycobacterium tuberculosis Is Crucial for Its Oligomerization and Function

Mycobacterium tuberculosis ClpC1 is a member of the Hsp100/Clp AAA+ family of ATPases. The primary sequence of ClpC1 contains two N-terminal domains and two nucleotide binding domains (NBD). The second NBD has a long C-terminal sub-domain containing several motifs important for substrate interaction. Generally, ClpC proteins are highly conserved, however presence of C-terminal domains of variable lengths is a remarkable difference in ClpC from different species. In this study, we constructed deletion mutants at the C-terminus of M. tuberculosis ClpC1 to determine its role in the structure and function of the protein. In addition, a deletion mutant having the two conserved N-terminal domains deleted was also constructed to investigate the role of these domains in M. tuberculosis ClpC1 function. The N-terminal domains were found to be dispensable for the formation of oligomeric structure, and ATPase and chaperone activities. However, deletions beyond a specific region in the C-terminus of the ClpC1 resulted in oligomerization defects and loss of chaperonic activity of the protein without affecting its ATPase activity. The truncated mutants, defective in oligomerization were also found to have lost the chaperonic activity, showing the formation of oligomer to be required for the chaperonic activity of M. tuberculosis ClpC1. The current study has identified a region in the C-terminus of M. tuberculosis ClpC1 which is essential for its oligomerization and in turn its function.     

On the macro-micro-morphology of organs of host invasion in hemiparasite Helicanthes elasticus (Desv.) Danser

Loranthaceae family includes hemiparasitic members which are seen invading a wide range of commercial crops. Helicanthes elasticus (Desv.) Danser is very common on mango trees. Though parasitic in nature, this mistletoe is also medicinally important as fetoprotective, against vesicular calculi and kidney infections. This study is an attempt to document macro-microscopical features of parasitic root, fruit and host-mistletoe tissue interaction in the haustorium of H. elasticus growing on mango stems. Collection, preservation, sectioning, staining and photomicrography of the root, fruit and host-mistletoe union were done as per standard methodologies of anatomical studies. Though there is resemblance to the normal roots in morphology as well as anatomy, the microscopic finding of large number of branched stone cells in the roots is interesting. The morpho-anatomical features recorded would help in understanding the infection biology of this mistletoe. The eradication during the earlier stages of its establishment from seed or from the root creeping over the surface of the host can help in controlling this parasite infection on commercially important host plants.     

Chemoenzymatic Synthesis of 3′-Deoxy-3′-(4-Substituted-Triazol-1-YL)-5-Methyluridine

An efficient protocol has been developed for the synthesis of a small library of 3′-deoxy-3′-(4-substituted-triazol-1-yl)-5-methyluridine using Cu(I)-catalyzed Huisgen–Sharpless–Meldal 1,3-dipolar cycloaddition reaction of 3′-azido-3′-deoxy-5-methyluridine with different alkynes under optimized condition in an overall yields of 76%–92%. Here, the azido precursor compound, i.e., 3′-azido-3′-deoxy-5-methyluridine was chemoenzymatically synthesized from D-xylose in good yield. Some of the alkynes used in cycloaddition reaction were synthesized by the reaction of hydroxycoumarins or naphthols with propargyl bromide in acetone using K₂CO₃in excellent yields. All synthesized compounds were unambiguously identified on the basis of their spectral (IR, ¹H-, ¹³C NMR spectra, and high-resolution mass spectra) data analysis.