Structure and dynamics of the N-terminal loop of PsbQ from photosystem II of Spinacia oleracea

Infrared and Raman spectroscopy were applied to identify restraints for the structure determination of the 20 amino acid loop between two beta-sheets of the N-terminal region of the PsbQ protein of the oxygen evolving complex of photosystem II from Spinacia oleracea by restraint-based homology modeling. One of the initial models has shown a stable fold of the loop in a 20 ns molecular dynamics simulation that is in accordance with spectroscopic data. Cleavage of the first 12 amino acids leads to a permanent drift in the root means square deviation of the protein backbone and induces major structural changes.     

Mitochondrial diseases and genetic defects of ATP synthase

ATP synthase is a key enzyme of mitochondrial energy conversion. In mammals, it produces most of cellular ATP. Alteration of ATP synthase biogenesis may cause two types of isolated defects: qualitative when the enzyme is structurally modified and does not function properly, and quantitative when it is present in insufficient amounts. In both cases the cellular energy provision is impaired, and diminished use of mitochondrial DeltamuH+ promotes ROS production by the mitochondrial respiratory chain. The primary genetic defects have so far been localized in mtDNA ATP6 gene and nuclear ATP12 gene, however, involvement of other nuclear genes is highly probable.     

Penetration of Trichobilharzia cercariae into mammals: dangerous or negligible event?

Bird schistosomes and cases of human cercarial dermatitis occur worldwide, but the number of cases is not monitored. Experiments with two schistosomes, namely Trichobilharzia szidati and T. regenti, show that they possess potent tools to penetration bird and mammalian skin, as well as exhibit species-specific migration patterns within vertebrate bodies. Therefore, the infections may affect different organs/tissues e.g. lungs or spinal cord. In this minireview, the adaptations and pathogenic effects of bird schistosomes in experimental mammals are discussed, and some ideas/hypotheses on risks to humans from exposure to bird schistosome cercariae are expressed.     

Liquid chromatography-tandem mass spectrometry characterization of ergocristam degradation products

The UPLC method with diode array UV detection was developed for qualitative determination of ergocristine and ergocristam including degradation products. The mechanism of the ergocristam disruptive reaction was described based on MS/MS characterization of ammonolytic product, N-(d-lysergyl)-l-valinamide (A1) and two methanolytic products, methyl ester of N-(d-lysergyl)-l-valine (M2), and N-[N-(d-lysergyl)-l-valyl]-l-phenylalanyl-d-prolyl methyl ester (M1). The influence of extraction conditions on epimerization and degradation of ergocristine and ergocristam was tested and conditions for reproducible decomposition of ergocristam were found. The presented method could potentially be applied for ergot alkaloids determination in sclerotia, fermentation broth, mycelium, and possibly contaminated food products, i.e. corn, flour, bread, etc., and feeding stuffs containing ungrounded cereals.     

Late blood pressure reduction in SHR subjected to transient captopril treatment in youth: possible mechanisms

Spontaneously hypertensive rats (SHR) are characterized by enhanced nifedipine-sensitive component of sympathetic vasoconstriction. Our study tried to elucidate the mechanisms responsible for long-term reduction of blood pressure (BP) in SHR subjected to early transient captopril treatment. Adult untreated SHR aged 30-34 weeks were compared with animals subjected to chronic captopril treatment for 6 weeks either in youth (between 4 and 10 weeks of age) or in adulthood (between 24 and 30 weeks of age). Antihypertensive effects of captopril were more pronounced in young than adult SHR. This was due to greater attenuation of sympathetic and nifedipine-sensitive BP components and prevention of residual BP rise in young captopril-treated SHR in which the reductions of nifedipine-sensitive BP component and residual BP persisted for 20 weeks after captopril withdrawal. The magnitude of nifedipine-sensitive component of sympathetic vasoconstriction is decisive for BP maintenance not only in untreated SHR but also in SHR during active captopril treatment by or after its withdrawal.     

Lateralization of hippocampal nitric oxide mediator system in people with Alzheimer disease, multi-infarct dementia and schizophrenia

There is evidence that brain lateralization underlying hemispheric specialization can be observed also at biochemical level. However, hemispheric differences in nitric oxide mediator system have not yet been evaluated. The hippocampus and planum temporale are highly asymmetrical regions but the degree of their laterality is altered in demented or psychotic people. In the study, l-glutamate/l-arginine/l-citrulline concentrations, nitric oxide synthase activities/expressions and nitrites/nitrates levels were estimated in autoptic hippocampi. Right/left laterality in endothelial synthase activity and in nitrites/nitrates was observed in controls. Lateral changes were estimated in patients with Alzheimer disease (a marked increase in activities of constitutive synthases and in expression of inducible enzyme in the left side) and schizophrenia (an increase in activities of all enzymes especially in the right side). Significant shifts from positive to negative correlations were found between laterality of some components of nitric oxide pathway and of planum temporale volumetry under pathological conditions. The hippocampal nitric oxide system appears to be globally right/left lateralized, especially via actions of highly asymmetrical endothelial synthase. The results suggest a specific involvement of all synthases in the development of selected diseases and show that lateral analyses are of sufficient sensitivity to reveal subtle links. The volumetric asymmetry of the planum temporale as a marker of handedness is not probably simply linked to brain laterality at biochemical level but reflects alterations due to pathological processes.     

The multiple T-maze in vivo testing of the neuroprotective effect of humanin analogues

Humanin (HN) and its analogues have been shown to protect cells against death induced by various Alzheimer's disease (AD) genes and amyloid-beta-peptides in vitro; the analogues [Gly(14)]-HN and colivelin have also been shown to be potent in reversing learning and memory impairment induced by scopolamine or quinuclidinyl benzilate (QNB) in mice or rats in vivo using the Y-maze or multiple T-maze tests. This paper describes the activity of new peptides of the HN family, after i.p. administration, on QNB-induced impairment of spatial memory in the multiple T-maze test in rats. The following peptides have been studied: HN analogues truncated either on the C- or N-terminus, or analogues having a tert-Leu in place of Leu in the central part of the molecule, the active HN core PAGASRLLLLTGEIDLP (RG-PAGA) and its analogues having three or five leucines instead of four, and finally the recently described hybrid peptide colivelin (i.e. a peptide having the activity-dependent neurotrophic factor SALLRSIPA attached to the N-terminus of the active RG-PAGA) and its des-Leu- and plus-Leu-analogues. While the truncated analogues and most of the tert-Leu containing analogues were devoid of activity, the analogues of the RG-PAGA were active, i.e. they reversed the impairment of spatial memory irrespective of the number of Leu present in their sequence. The highest activity was shown by colivelin and its des-Leu-analogue. These results demonstrate the potential of HN analogues in the modulation of the cholinergic system, which plays an important role in the cognitive deficits associated with AD and other neurodegenerative diseases.     

Cationic amino acid transport across the blood-brain barrier is mediated exclusively by system y+

Cationic amino acid (CAA) transport is brought about by two families of proteins that are found in various tissues: Cat (CAA transporter), referred to as system y+, and Bat [broad-scope amino acid (AA) transporter], which comprises systems b0,+, B0,+, and y+L. CAA traverse the blood-brain barrier (BBB), but experiments done in vivo have only been able to examine the BBB from the luminal (blood-facing) side. In the present study, plasma membranes isolated from bovine brain microvessels were used to identify and characterize the CAA transporter(s) on both sides of the BBB. From these studies, it was concluded that system y+ was the only transporter present, with a prevalence of activity on the abluminal membrane. System y+ was voltage dependent and had a Km of 470 +/- 106 microM (SE) for lysine, a Ki of 34 microM for arginine, and a Ki of 290 microM for ornithine. In the presence of Na+, system y+ was inhibited by several essential neutral AAs. The Ki values were 3-10 times the plasma concentrations, suggesting that system y+ was not as important a point of access for these AAs as system L1. Several small nonessential AAs (serine, glutamine, alanine,and glycine) inhibited system y+ with Ki values similar to their plasma concentrations, suggesting that system y+ may account for the permeability of the BBB to these AAs. System y+ may be important in the provision of arginine for NO synthesis. Real-time PCR and Western blotting techniques established the presence of the three known nitric oxide synthases in cerebral endothelial cells: NOS-1 (neuronal), NOS-2 (inducible), and NOS-3 (endothelial). These results confirm that system y+ is the only CAA transporter in the BBB and suggest that NO can be produced in brain endothelial cells.     

A directed screen for chlamydial proteins secreted by a type III mechanism identifies a translocated protein and numerous other new candidates

Chlamydiae are strict intracellular parasites that induce their internalization upon contact with the host cell and grow inside an intracellular compartment called an inclusion. They possess a type III secretion (TTS) apparatus, which allows for the translocation of specific proteins in the host cell cytosol. In particular, chlamydial proteins of the Inc family are secreted to the inclusion membrane by a TTS mechanism; other TTS substrates are mostly unknown. Using a secretion assay based on the recognition of TTS signals in Shigella flexneri, we searched for TTS signals in the proteins of unknown function, conserved between three different chlamydial species, Chlamydia pneumoniae, C. trachomatis and C. caviae. We identified 24 new candidate proteins which did not belong to the Inc family. Four of these proteins were also secreted as full-length proteins by a TTS mechanism in S. flexneri, indicating that their translocation does not require other chlamydial proteins. One of these proteins was detected in the cytosol of infected cells using specific antibodies, directly demonstrating that it is translocated in the host cell during bacterial proliferation. More generally, this work represents the first directed search for TTS effectors not based on genetic information or sequence similarity. It reveals the abundance of proteins secreted in the host cell by chlamydiae.