Interaction of Aryl Hydrocarbon Receptor-interacting Protein-like 1 with the Farnesyl Moiety

Aryl hydrocarbon receptor-interacting protein-like 1 (AIPL1) is a photoreceptor specific chaperone of the visual effector enzyme phosphodiesterase-6 (PDE6). AIPL1 has been shown to bind the farnesylated PDE6A subunit. Mutations in AIPL1 are thought to destabilize PDE6 and thereby cause Leber congenital amaurosis type 4 (LCA4), a severe form of childhood blindness. Here, we examined the solution structure of AIPL1 by small angle x-ray scattering. A structural model of AIPL1 with the best fit to the scattering data features two independent FK506-binding protein (FKBP)-like and tetratricopeptide repeat domains. Guided by the model, we tested the hypothesis that AIPL1 directly binds the farnesyl moiety. Our studies revealed high affinity binding of the farnesylated-Cys probe to the FKBP-like domain of AIPL1, thus uncovering a novel function of this domain. Mutational analysis of the potential farnesyl-binding sites on AIPL1 identified two critical residues, Cys-89 and Leu-147, located in close proximity in the structure model. The L147A mutation and the LCA-linked C89R mutation prevented the binding of the farnesyl-Cys probe to AIPL1. Furthermore, Cys-89 and Leu-147 flank the unique insert region of AIPL1, deletion of which also abolished the farnesyl interaction. Our results suggest that the binding of PDE6A farnesyl is essential to normal function of AIPL1 and its disruption is one of the mechanisms underlying LCA.     

Evaluation of Memory Enhancing Clinically Available Standardized Extract of Bacopa monniera on P-Glycoprotein and Cytochrome P450 3A in Sprague-Dawley Rats

Bacopa monniera is a traditional Ayurvedic herbal medicine used to treat various mental ailments from ancient times. Recently, chemically standardized alcoholic extract of Bacopa monniera (BM) has been developed and currently available as over the counter herbal remedy for memory enhancement in children and adults. However, the consumption of herbal drugs has been reported to alter the expression of drug metabolizing enzymes and membrane transporters. Present study in male Sprague-Dawley rat was performed to evaluate the effect of memory enhancing standardized extract of BM on hepatic and intestinal cytochrome P450 3A and P-glycoprotein expression and activity. The BM (31 mg/kg/day) was orally administered for one week in BM pre-treated group while the control group received the same amount of vehicle for the same time period. The BM treatment decreased the cytochrome P450 3A (CYP3A) mediated testosterone 6β-hydroxylation activity of the liver and intestine by 2 and 1.5 fold, respectively compared to vehicle treated control. Similarly pretreatment with BM extract decreased the expression of intestinal P-glycoprotein (Pgp) as confirmed by Western blot analysis but did not alter the expression of hepatic Pgp. To investigate whether this BM pretreatment mediated decrease in activity of CYP3A and Pgp would account for the alteration of respective substrate or not, pharmacokinetic study with carbamazepine and digoxin was performed in BM pre-treated rats and vehicle treated rats. Carbamazepine and digoxin were used as CYP3A and Pgp probe drugs, respectively. Significant increase in AUC and Cmax of carbamazepine (4 and 1.8 fold) and digoxin (1.3 and 1.2 fold), respectively following the BM pre-treatment confirmed the down regulation of CYP3A and Pgp.     

The type III secretion system needle,tip, and translocon

Many Gram‐negative bacteria pathogenic to plants and animals deploy the type III secretion system (T3SS) to inject virulence factors into their hosts. All bacteria that rely on the T3SS to cause infectious diseases in humans have developed antibiotic resistance. The T3SS is an attractive target for developing new antibiotics because it is essential in virulence, and part of its structural component is exposed on the bacterial surface. The structural component of the T3SS is the needle apparatus, which is assembled from over 20 different proteins and consists of a base, an extracellular needle, a tip, and a translocon. This review summarizes the current knowledge on the structure and assembly of the needle, tip, and translocon.     

Weighted average regression and environmental calibration as a tool for quantifying climate-driven changes in vegetation

Aims Studies of the climatic responses of plant assemblages via vegetation-based environmental reconstructions by weighted averaging (WA) regression and calibration are a recent development in modern vegetation ecology. However, the performance of this technique for plot-based vegetation datasets has not been rigorously tested. We assess the estimation accuracy of the WA approach by comparing results, mainly the root mean square error of prediction (RMSEP) of WA regressions for six different vegetation datasets (total species, high-frequency species and low-frequency species as both abundance and incidence) each from two sites.     

Clade 8 and Clade 6 Strains of Escherichia coli O157:H7 from Cattle in Argentina have Hypervirulent-Like Phenotypes

The hemolytic uremic syndrome (HUS) whose main causative agent is enterohemorrhagic Escherichia coli (EHEC) O157:H7 is a disease that mainly affects children under 5 years of age. Argentina is the country with the highest incidence of HUS in the world. Cattle are a major reservoir and source of infection with E. coli O157:H7. To date, the epidemiological factors that contribute to its prevalence are poorly understood. Single nucleotide polymorphism (SNP) typing has helped to define nine E. coli O157:H7 clades and the clade 8 strains were associated with most of the cases of severe disease. In this study, eight randomly selected isolates of EHEC O157:H7 from cattle in Argentina were studied as well as two human isolates. Four of them were classified as clade 8 through the screening for 23 SNPs; the two human isolates grouped in this clade as well, while two strains were closely related to strains representing clade 6. To assess the pathogenicity of these strains, we assayed correlates of virulence. Shiga toxin production was determined by an ELISA kit. Four strains were high producers and one of these strains that belonged to a novel genotype showed high verocytotoxic activity in cultured cells. Also, these clade 8 and 6 strains showed high RBC lysis and adherence to epithelial cells. One of the clade 6 strains showed stronger inhibition of normal water absorption than E. coli O157:H7 EDL933 in human colonic explants. In addition, two of the strains showing high levels of Stx2 production and RBC lysis activity were associated with lethality and uremia in a mouse model. Consequently, circulation of such strains in cattle may partially contribute to the high incidence of HUS in Argentina.     

Maximizing power generation from dark fermentation effluents in microbial fuel cell by selective enrichment of exoelectrogens and optimization of anodic operational parameters

Objective

To selectively enrich an electrogenic mixed consortium capable of utilizing dark fermentative effluents as substrates in microbial fuel cells and to further enhance the power outputs by optimization of influential anodic operational parameters.

Results

A maximum power density of 1.4 W/m³ was obtained by an enriched mixed electrogenic consortium in microbial fuel cells using acetate as substrate. This was further increased to 5.43 W/m³ by optimization of influential anodic parameters. By utilizing dark fermentative effluents as substrates, the maximum power densities ranged from 5.2 to 6.2 W/m³ with an average COD removal efficiency of 75% and a columbic efficiency of 10.6%.

Conclusion

A simple strategy is provided for selective enrichment of electrogenic bacteria that can be used in microbial fuel cells for generating power from various dark fermentative effluents.