Porphyrin Binding to Gun4 Protein,Facilitated by a Flexible Loop,Controls Metabolite Flow through the Chlorophyll Biosynthetic Pathway

In oxygenic phototrophs, chlorophylls, hemes, and bilins are synthesized by a common branched pathway. Given the phototoxic nature of tetrapyrroles, this pathway must be tightly regulated, and an important regulatory role is attributed to magnesium chelatase enzyme at the branching between the heme and chlorophyll pathway. Gun4 is a porphyrin-binding protein known to stimulate in vitro the magnesium chelatase activity, but how the Gun4-porphyrin complex acts in the cell was unknown. To address this issue, we first performed simulations to determine the porphyrin-docking mechanism to the cyanobacterial Gun4 structure. After correcting crystallographic loop contacts, we determined the binding site for magnesium protoporphyrin IX. Molecular modeling revealed that the orientation of α6/α7 loop is critical for the binding, and the magnesium ion held within the porphyrin is coordinated by Asn-211 residue. We also identified the basis for stronger binding in the Gun4-1 variant and for weaker binding in the W192A mutant. The W192A-Gun4 was further characterized in magnesium chelatase assay showing that tight porphyrin binding in Gun4 facilitates its interaction with the magnesium chelatase ChlH subunit. Finally, we introduced the W192A mutation into cells and show that the Gun4-porphyrin complex is important for the accumulation of ChlH and for channeling metabolites into the chlorophyll biosynthetic pathway.     

Conformational Response to Ligand Binding in Phosphomannomutase2: INSIGHTS INTO INBORN GLYCOSYLATION DISORDER*

The most common glycosylation disorder is caused by mutations in the gene encoding phosphomannomutase2, producing a disease still without a cure. Phosphomannomutase2, a homodimer in which each chain is composed of two domains, requires a bisphosphate sugar (either mannose or glucose) as activator, opening a possible drug design path for therapeutic purposes. The crystal structure of human phosphomannomutase2, however, lacks bound substrate and a key active site loop. To speed up drug discovery, we present here the first structural model of a bisphosphate substrate bound to human phosphomannomutase2. Taking advantage of recent developments in all-atom simulation techniques in combination with limited and site-directed proteolysis, we demonstrated that α-glucose 1,6-bisphosphate can adopt two low energy orientations as required for catalysis. Upon ligand binding, the two domains come close, making the protein more compact, in analogy to the enzyme in the crystals from Leishmania mexicana. Moreover, proteolysis was also carried out on two common mutants, R141H and F119L. It was an unexpected finding that the mutant most frequently found in patients, R141H, although inactive, does bind α-glucose 1,6-bisphosphate and changes conformation.     

Adaptación y validación de la versión española de la escala de evaluación de dolor en personas con demencia avanzada: PAINAD-Sp

Introduction

Pain in elderly people is considered a major concern in nursing home facilities affecting between 49% and 83% of the residents. Progression of Alzheimer's Disease causes more communication difficulties in patients with advanced dementia and therefore more problems to understand even the most simple pain evaluation scales. Identification and implementation of appropriate pain management strategies depends on an adequate pain assessment.

Material and methods

The main objective of the study was to validate the Spanish version of the PAINAD Scale (PAINAD-Sp) and to assess its applicability in Spanish Geriatric Nursing Homes. The 20 patients diagnosed with severe dementia from a Geriatric Centre in Spain were observed by five observers with different professional profiles for 5 minutes to each participant, and PAINAD-Sp Scale was administered simultaneously to a Visual Analogical Scale-VAS. Three different observational conditions were established: resting condition, during presumably pleasant activity and during presumable painful activity.

Results

Cronbach's alpha ranged between 0.467 and 0.827 (average 0.692), and rose if Breathing item was deleted. Inter-rater reliability ranged between 0.587 and 0.956. Correlation between PAINAD-Sp Scale total measures and VAS was statistically significant (P<.05) in all measures and ranged from 0.517 to 0.868.

Conclusions

Findings in the study showed that the scale is useful to measure pain in non communicative patients suffering from dementia. The scale maintains good levels of reliability for different healthcare professionals even when they have little training.     

One-step synthesis of isomalto-oligosaccharide syrups and dextrans of controlled size using engineered dextransucrase

Isomalto-oligosaccharides and dextrans of controlled molecular weight of about 10 and 40 kDa were produced using a simple one-step process using engineered L. mesenteroides NRRL B-512F dextransucrase variants. Isomalto-oligosaccharides were produced in a 58% yield by the acceptor reaction with glucose, and reached a degree of polymerization of at least 27 glucosyl units. Reaction conditions for optimal synthesis of dextrans of controlled molecular weight were defined, in respect of initial sucrose concentration and reaction temperature. Thus, we achieved synthesis with impressive yields of 69 and 75% for the 40 and 10 kDa dextran species, respectively. These two dextran sizes are particularly suitable for clinical applications, and are of great industrial demand. Compared with the traditional processes based on chemical hydrolysis and fractionation, which achieve only low yields, the new enzymatic methods offer improvement in quantity, quality and efficiency.     

STIM1 converts TRPC1 from a receptor-operated to a store-operated channel: moving TRPC1 in and out of lipid rafts

While the role of members from the TRPC family of channels as receptor-operated channels (ROC) is well established and supported by numerous studies, the role of this family of channels as store-operated channels (SOC) has been the focus of a heated controversy over the last few years. In the present study, we have explored the modulation of STIM1 on human TRPC1 channel. We show that the association of STIM1 to TRPC1 favors the insertion of TRPC1 into lipid rafts, where TRPC1 functions as a SOC. In the absence of STIM1, TRPC1 associates to other members from the TRPC family of channels to form ROCs. A novel TIRFM-FRET method illustrates the relevance of the dynamic association between STIM1 and TRPC1 for the activation of SOC and the lipid raft localization of the STIM1-TRPC1 complex. This study provides new evidence about the dual activity of TRPC1 (forming ROC or SOC) and the partners needed to determine TRPC1 functional fate. It highlights also the role of plasma membrane microdomains and ER-PM junctions in modulating TRPC1 channel function and its association to STIM1.     

Impact of long-term treatment with ivermectin on the prevalence and intensity of soil-transmitted helminth infections

Background

Control of soil-transmitted helminth (STH) infections relies on the periodic and long-term administration of anthelmintic drugs to high-risk groups, particularly school-age children living in endemic areas. There is limited data on the effectiveness of long-term periodic anthelmintic treatment on the prevalence of STHs, particularly from operational programmes. The current study investigated the impact of 15 to 17 years of treatment with the broad-spectrum anthelmintic ivermectin, used for the control of onchocerciasis, on STH prevalence and intensity in school-age and pre-school children.

Methods and Findings

A cross-sectional study was conducted in communities that had received annual or twice-annual ivermectin treatments and geographically adjacent communities that had not received treatment in two districts of Esmeraldas Province in Ecuador. Stool samples were collected from school-age children and examined for STH infection using the Kato-Katz and formol-ether concentration methods. Samples were collected also from pre-school children and examined by the formol-ether concentration method. Data on risk factors for STH infection were collected by parental questionnaire. We sampled a total of 3,705 school-age children (6–16 years) from 31 treated and 27 non-treated communities, and 1,701 pre-school children aged 0–5 years from 18 treated and 18 non-treated communities. Among school-age children, ivermectin treatment had significant effects on the prevalence (adjusted OR =  0.06, 95% CI 0.03–0.14) and intensity of Trichuris trichiura infection (adjusted RR = 0.28, 95% CI 0.11–0.70), but appeared to have no impact on Ascaris lumbricoides or hookworm infection. Reduced prevalence and intensities of T. trichiura infection were observed among children not eligible to receive ivermectina, providing some evidence of reduced transmission of T. trichiura infection in communities receiving mass ivermectin treatments.

Conclusion

Annual and twice-annual treatments with ivermectin over a period of up to 17 years may have had a significant impact on T. trichiura infection. The present data indicate that the long-term control of onchocerciasis with ivermectin may provide additional health benefits by reducing infections with trichuriasis. The addition of a second anthelmintic drug such as albendazole may be useful for a long-term effect on A. lumbricoides infection.     

Anaerobic energy provision does not limit Wingate exercise performance in endurance-trained cyclists.

The aim of this study was to evaluate the effects of severe acute hypoxia on exercise performance and metabolism during 30-s Wingate tests. Five endurance- (E) and five sprint- (S) trained track cyclists from the Spanish National Team performed 30-s Wingate tests in normoxia and hypoxia (inspired O(2) fraction = 0.10). Oxygen deficit was estimated from submaximal cycling economy tests by use of a nonlinear model. E cyclists showed higher maximal O(2) uptake than S (72 +/- 1 and 62 +/- 2 ml x kg(-1) x min(-1), P < 0.05). S cyclists achieved higher peak and mean power output, and 33% larger oxygen deficit than E (P < 0.05). During the Wingate test in normoxia, S relied more on anaerobic energy sources than E (P < 0.05); however, S showed a larger fatigue index in both conditions (P < 0.05). Compared with normoxia, hypoxia lowered O(2) uptake by 16% in E and S (P < 0.05). Peak power output, fatigue index, and exercise femoral vein blood lactate concentration were not altered by hypoxia in any group. Endurance cyclists, unlike S, maintained their mean power output in hypoxia by increasing their anaerobic energy production, as shown by 7% greater oxygen deficit and 11% higher postexercise lactate concentration. In conclusion, performance during 30-s Wingate tests in severe acute hypoxia is maintained or barely reduced owing to the enhancement of the anaerobic energy release. The effect of severe acute hypoxia on supramaximal exercise performance depends on training background.     

Neurospora crassa mutant impaired in glutamine regulation.

The final products of the catabolism of arginine that can be utilized as nitrogen sources by Neurospora crassa are ammonium, glutamic acid, and glutamine. Of these compounds, only glutamine represses arginase and glutamine synthetase. We report here the isolation and characterization of a mutant of N. crassa whose arginase, glutamine synthetase, and amino acid accumulations are resistant to glutamine repression (glnI). This mutant has a greater capacity than the wild type (glns) to accumulate most of the arginine and some of the glutamine in osmotically sensitive compartments while growing exponentially. Nonetheless, the major part of the glutamine remains soluble and metabolically available for repression. We propose that the lower repression of glutamine synthetase by glutamine in this mutant could be a necessary condition for sustaining the higher flow of nitrogen for the accumulation of amino acids observed in ammonium excess and that, if glutamine is the nitrogen signal that regulates the arginine accumulation of the vesicle, the glnr mutant has also escaped this control. Finally, in the glnr mutant, some glutamine resynthesis is necessary for arginine biosynthesis and accumulation.     

Meiotic arrest at first spermatocyte level: A new inherited infertility disorder

Summary Three 46,XY phenotypically male, azoospermic brothers out of thirteen sibs from a consanguineous marriage were studied and found to have a unique pattern of testicular histology with arrest of spermatogenesis at the pachytene stage of primary spermatocytes. Endocrinological evaluation showed elevated plasma luteinizing (LH) and normal to elevated follicle-stimulating (FSH) hormones, positive gonadotropin pituitary response to luteinizing hormone-releasing hormone, depletion of LH and FSH levels by exogenous testosterone (T) administration, normal levels of T and dihydrotestosterone hormones, and elevation of T after stimulation with human chorionic gonadotropin hormone. Electrophoretic assay of lactic dehydrogenase isozymes did not reveal band C₄ in semen or testicular tissue. These traits seem to constitute a hitherto undescribed form of infertility in which spermatogenesis arrest at the first spermatocyte level is the main feature. The parental consanguinity suggests autosomal recessive inheritance.