Sulfur regulation of the sulfate transporter genes sutA and sutB in Penicillium chrysogenum

Penicillium chrysogenum uses sulfate as a source of sulfur for the biosynthesis of penicillin. Sulfate uptake and the mRNA levels of the sulfate transporter-encoding sutB and sutA genes are all reduced by high sulfate concentrations and are elevated by sulfate starvation. In a high-penicillin-yielding strain, sutB is effectively transcribed even in the presence of excess sulfate. This deregulation may facilitate the efficient incorporation of sulfur into cysteine and penicillin.     

Apolipoprotein E4 and memory decline in the elderly

The objective of this study was to investigate whether the association between Apolipoprotein E4 (ApoE4) and memory decline is modified by baseline general cognitive impairment and age in a population-based elderly sample. Subjects were participants in the Longitudinal Aging Study Amsterdam (LASA). The study sample consisted of 1,243 subjects, 62-85 years old, with a Mini-Mental State Examination (MMSE) score between 21-30 and known ApoE phenotypes. Memory performance was measured with a short version of the Auditory Verbal Learning Test (AVLT) at baseline and repeated after three years (N = 854). Memory decline was defined as a decrease of at least one standard deviation from the mean change score on immediate recall, delayed recall and retention. ApoE4 was associated with memory decline in cognitively impaired subjects (MMSE 21-26), but not in cognitively normal subjects (MMSE 27-30). In particular cognitively impaired E4 carriers older than 75 years were at high risk of memory decline. Contrary to AD studies, our study suggests that the risk of ApoE4 on memory decline does not decrease with ageing.     

Changes in luminal pH caused by calcium release in sarcoplasmic reticulum vesicles.

Fast (milliseconds) Ca2+ release from sarcoplasmic reticulum is an essential step in muscle contraction. To electrically compensate the charge deficit generated by calcium release, concomitant fluxes of other ions are required. In this study we investigated the possible participation of protons as counterions during calcium release. Triad-enriched sarcoplasmic reticulum vesicles, isolated from rabbit fast skeletal muscle, were passively loaded with 1 mM CaCl2 and release was induced at pCa = 5.0 and pH = 7.0 in a stopped-flow fluorimeter. Accompanying changes in vesicular lumen pH were measured with a trapped fluorescent pH indicator (pyranin). Significant acidification (approximately 0.2 pH units) of the lumen occurred within the same time scale (t(1/2) = 0.75 s) as calcium release. Enhancing calcium release with ATP or the ATP analog 5'-adenylylimidodiphosphate (AMPPNP) produced >20-fold faster acidification rates. In contrast, when calcium release induced with calcium with or without AMPPNP was blocked by Mg2+, no acidification of the lumen was observed. In all cases, rate constants of luminal acidification corresponded with reported values of calcium release rate constants. We conclude that proton fluxes account for part (5-10%) of the necessary charge compensation during calcium release. The possible relevance of these findings to the physiology of muscle cells is discussed.     

Evidence for a Regulatory Link of Nitrogen Fixation and Photosynthesis in Rhodobacter capsulatus via HvrA

A Rhodobacter capsulatus reporter strain, carrying a constitutively expressed nifA gene and a nifH-lacZ gene fusion, was used for random transposon Tn5 mutagenesis to search for genes required for the NtrC-independent ammonium repression of NifA activity. A mutation in hvrA, which is known to be involved in low-light activation of the photosynthetic apparatus, released both ammonium and oxygen control of nifH expression in this reporter strain, demonstrating a regulatory link of nitrogen fixation and photosynthesis via HvrA. In addition, a significant increase in bacteriochlorophyll a (BChla) content was found in cells under nitrogen-fixing conditions. HvrA was not involved in this up-regulation of BChla. Instead, the presence of active nitrogenase seemed to be sufficient for this process, since no increase in BChla content was observed in different nif mutants.     

Phylogenetic and Functional Classification of Mitogen- and Stress-Activated Protein Kinases

All currently sequenced stress-activated protein kinases (SAPKs), extracellular signal-regulated kinases (ERKs), and other mitogen-activated protein kinases (MAPKs) were analyzed by sequence alignment, phylogenetic tree construction, and three-dimensional structure modeling in order to classify members of the MAPK family. Based on this analysis the MAPK family was divided into three subgroups (SAPKs, ERKs, and MAPK3) that consist of at least nine subfamilies. Members of a given subfamily were exclusively from animals, plants, or yeast/fungi. A single signature sequence, [LIVM][TS]XX[LIVM]XT[RK][WY]YRXPX[LIVM] [LIVM], was identified that is characteristic for all MAPKs and sufficient to distinguish MAPKs from other members of the protein kinase superfamily. This signature sequence contains the phosphorylation site and is located on loop 12 of the three-dimensional structure of MAPKs. I also identified signature sequences that are characteristic for each of the nine subfamilies of MAPKs. By modeling the three-dimensional structure of three proteins for each MAPK subfamily based on the resolved atomic structures of rat ERK2 and murine p38, it is demonstrated that amino acids conserved in all MAPKs are located primarily in the center of the protein around the catalytic cleft. I conclude that these residues are important for maintaining proper folding into the gross structure common to all MAPKs. On the other hand, amino acids conserved in a given subfamily are located mainly in the periphery of MAPKs, indicating their possible importance for defining interactions with substrates, activators, and inhibitors. Within these subfamily-specific regions, amino acids were identified that represent unique residues occurring in only a single subfamily and their location was mapped in three-dimensional structure models. These unique residues are likely to be crucial for subfamily-specific interactions of MAPKs with substrates, inhibitors, or activators and, therefore, represent excellent targets for site-directed mutagenesis experiments. Received: 13 August 1997 / Accepted: 21 November 1997     

Allene oxide synthase: a major control point in Arabidopsis thaliana octadecanoid signalling

The analysis of allene oxide synthase (AOS) mRNA levels, of AOS polypeptide levels and specific enzymatic activities, as well as the quantitative determination of the levels of the octadecanoids cis-12-oxophytodienoic acid (cis-OPDA) and JA following a number of treatments, has shown that AOS is a regulatory site in octadecanoid biosynthesis in A. thaliana. AOS activity, mRNA and polypeptide levels are increased in wounded leaves locally and systemically. The methyl esters of OPDA or JA (OPDAME, JAME) and coronatine, are strong inducers of AOS mRNA, polypeptide and enzymatic activity. Ethephon also induces AOS activity. Salicylic acid (SA) was an inducer of AOS activity while abscisic acid (ABA) had no effect. At the level of the octadecanoids, the consequences of induction of AOS by the different inducers were distinctly different, depending on the nature of the inducer. Wounding led to a strong, bi-phasic accumulation of JA in wounded leaves and to a less pronounced increase in JA-levels in systemic leaves. Levels of OPDA changed very little in wounded leaves and remained constant or even declined in systemic leaves. Ethephon treatment resulted in a strong, transient increase in JA-levels kinetically coinciding with the second, more pronounced peak in wound-induced JA. In SA-treated leaves, the level of cis-OPDA increased throughout the experimental period while there was no effect on JA levels during the first 24 h following treatment and only a slight accumulation after 48 h. Clearly, mechanisms in addition to regulating substrate (LA) availability and the regulation of AOS accumulation control the output of the octadecanoid pathway.     

ATP-synthesis in archaea: Structure-function relations of the halobacterial A-ATPase

The archaeal (A)-ATPase has been described as a chimeric energy converter with close relationship to both the vacuolar ATPase class in higher eukaryotes and the coupling factor (F)-ATPase class in eubacteria, mitochondria and chloroplasts. With respect to their structure and some inhibitor responses, A-ATPases are more closely related to the vacuolar ATPase type than to F-ATPase. Their function, ATP synthesis at the expense of an ion gradient, however, is a typical attribute of the F-ATPase class. V-type ATPases serve as generators of a proton gradient driving the accumulation of solutes within vesicles such as the vacuoles of plant cells. The three catalytic subunits (A) of the archaeal ATPases are the largest subunits of the A1-part and, like in V-ATPases, closer related to the F-ATPase -subunits, whereas B corresponds to F-ATPase . The catalytic subunits A of archaeal ATPases contain an insert of about 80 amino acids in their primary structures that may be aligned to comparable structures in V-ATPases. The location of this additional peptide in Haloferax volcanii is shown using the 2.8 Å X-ray resolution of the bovine mitochondrial F-ATPase [Abrahams et al. (1994) Nature 370: 621-628]. A three dimensional structure for the catalytic subunit of Haloferax volcanii ATPase is proposed using the Swiss-Model Automated Protein Modelling Server. The halobacterial ATPase is a halophilic protein; it contains about 20% negatively charged amino acid residues. A large portion of acidic residues is located on the outer surface of the protein as well as in the insert of subunit A. This result is discussed in terms of protein stability under high salt stress conditions.     

Alterations in the proteome of the respiratory tract in response to single and multiple exposures to naphthalene

Protein adduction is considered to be critical to the loss of cellular homeostasis associated with environmental chemicals undergoing metabolic activation. Despite considerable effort, our understanding of the key proteins mediating the pathologic consequences from protein modification by electrophiles is incomplete. This work focused on naphthalene (NA) induced acute injury of respiratory epithelial cells and tolerance which arises after multiple toxicant doses to define the initial cellular proteomic response and later protective actions related to tolerance. Airways and nasal olfactory epithelium from mice exposed to 15 ppm NA either for 4 h (acute) or for 4 h/day × 7 days (tolerant) were used for label‐free protein quantitation by LC/MS/MS. Cytochrome P450 2F2 and secretoglobin 1A1 are decreased dramatically in airways of mice exposed for 4 h, a finding consistent with the fact that CYPs are localized primarily in Clara cells. A number of heat shock proteins and protein disulfide isomerases, which had previously been identified as adduct targets for reactive metabolites from several lung toxicants, were upregulated in airways but not olfactory epithelium of tolerant mice. Protein targets that are upregulated in tolerance may be key players in the pathophysiology associated with reactive metabolite protein adduction. All MS data have been deposited in the ProteomeXchange with identifier PXD000846 ( http://proteomecentral.proteomexchange.org/dataset/PXD000846 ).     

Parental Use of Corporal Punishment in Europe: Intersection between Public Health and Policy

Studies have linked the use of corporal punishment of children to the development of mental health disorders. Despite the recommendation of international governing bodies for a complete ban of the practice, there is little European data available on the effects of corporal punishment on mental health and the influence of laws banning corporal punishment. Using data from the School Children Mental Health Europe survey, the objective of this cross-sectional study was to examine the prevalence and legal status of corporal punishment across six European countries and to evaluate the association between parental use of corporal punishment and children’s mental health. The study found that odds of having parents who reported using occasional to frequent corporal punishment were 1.7 times higher in countries where its use is legal, controlling for socio-demographic factors. Children with parents who reported using corporal punishment had higher rates of both externalized and internalized mental health disorders.     

The Golgi-Localized γ-Ear-Containing ARF-Binding (GGA) Proteins Alter Amyloid-β Precursor Protein (APP) Processing through Interaction of Their GAE Domain with the Beta-Site APP Cleaving Enzyme 1 (BACE1)

Proteolytic processing of amyloid-β precursor protein (APP) by beta-site APP cleaving enzyme 1 (BACE1) is the initial step in the production of amyloid beta (Aβ), which accumulates in senile plaques in Alzheimer’s disease (AD). Essential for this cleavage is the transport and sorting of both proteins through endosomal/Golgi compartments. Golgi-localized γ-ear-containing ARF-binding (GGA) proteins have striking cargo-sorting functions in these pathways. Recently, GGA1 and GGA3 were shown to interact with BACE1, to be expressed in neurons, and to be decreased in AD brain, whereas little is known about GGA2. Since GGA1 impacts Aβ generation by confining APP to the Golgi and perinuclear compartments, we tested whether all GGAs modulate BACE1 and APP transport and processing. We observed decreased levels of secreted APP alpha (sAPPα), sAPPβ, and Aβ upon GGA overexpression, which could be reverted by knockdown. GGA-BACE1 co-immunoprecipitation was impaired upon GGA-GAE but not VHS domain deletion. Autoinhibition of the GGA1-VHS domain was irrelevant for BACE1 interaction. Our data suggest that all three GGAs affect APP processing via the GGA-GAE domain.