Class-specific restrictions define primase interactions with DNA template and replicative helicase

Bacterial primase is stimulated by replicative helicase to produce RNA primers that are essential for DNA replication. To identify mechanisms regulating primase activity, we characterized primase initiation specificity and interactions with the replicative helicase for gram-positive Firmicutes (Staphylococcus, Bacillus and Geobacillus) and gram-negative Proteobacteria (Escherichia, Yersinia and Pseudomonas). Contributions of the primase zinc-binding domain, RNA polymerase domain and helicase-binding domain on de novo primer synthesis were determined using mutated, truncated, chimeric and wild-type primases. Key residues in the β4 strand of the primase zinc-binding domain defined class-associated trinucleotide recognition and substitution of these amino acids transferred specificity across classes. A change in template recognition provided functional evidence for interaction in trans between the zinc-binding domain and RNA polymerase domain of two separate primases. Helicase binding to the primase C-terminal helicase-binding domain modulated RNA primer length in a species-specific manner and productive interactions paralleled genetic relatedness. Results demonstrated that primase template specificity is conserved within a bacterial class, whereas the primase–helicase interaction has co-evolved within each species.     

G protein-coupled receptor systems and their lipid environment in health disorders during aging

Cells, tissues and organs undergo phenotypic changes and deteriorate as they age. Cell growth arrest and hyporesponsiveness to extrinsic stimuli are all hallmarks of senescent cells. Most such external stimuli received by a cell are processed by two different cell membrane systems: receptor tyrosine kinases (RTKs) and G protein-coupled receptors (GPCRs). GPCRs form the largest gene family in the human genome and they are involved in most relevant physiological functions. Given the changes observed in the expression and activity of GPCRs during aging, it is possible that these receptors are directly involved in aging and certain age-related pathologies. On the other hand, both GPCRs and G proteins are associated with the plasma membrane and since lipid-protein interactions regulate their activity, they can both be considered to be sensitive to the lipid environment. Changes in membrane lipid composition and structure have been described in aged cells and furthermore, these membrane changes have been associated with alterations in GPCR mediated signaling in some of the main health disorders in elderly subjects. Although senescence could be considered a physiologic process, not all aging humans develop the same health disorders. Here, we review the involvement of GPCRs and their lipid environment in the development of the major human pathologies associated with aging such as cancer, neurodegenerative disorders and cardiovascular pathologies.     

Hyperthermophilic Aquifex aeolicus initiates primer synthesis on a limited set of trinucleotides comprised of cytosines and guanines

The placement of the extreme thermophile Aquifex aeolicus in the bacterial phylogenetic tree has evoked much controversy. We investigated whether adaptations for growth at high temperatures would alter a key functional component of the replication machinery, specifically DnaG primase. Although the structure of bacterial primases is conserved, the trinucleotide initiation specificity for A. aeolicus was hypothesized to differ from other microbes as an adaptation to a geothermal milieu. To determine the full range of A. aeolicus primase activity, two oligonucleotides were designed that comprised all potential trinucleotide initiation sequences. One of the screening templates supported primer synthesis and the lengths of the resulting primers were used to predict possible initiation trinucleotides. Use of trinucleotide-specific templates demonstrated that the preferred initiation trinucleotide sequence for A. aeolicus primase was 5′-d(CCC)-3′. Two other sequences, 5′-d(GCC)-3′ and d(CGC)-3′, were also capable of supporting initiation, but to a much lesser degree. None of these trinucleotides were known to be recognition sequences used by other microbial primases. These results suggest that the initiation specificity of A. aeolicus primase may represent an adaptation to a thermophilic environment.     

Evidence of morphological and functional abnormalities in the hypothalamus of growth-hormone-deficient children: a combined magnetic resonance imaging and endocrine study

Fifty-seven children with growth hormone deficiency and 15 healthy age-matched controls were studied by magnetic resonance imaging (MRI). Of the patients, 36 (63%) had isolated GH deficiency (IGHD) and 21 (37%) multiple pituitary hormone deficiency (MPHD). MRI studies showed a marked reduction in pituitary volume in all patients in comparison with normal controls. Moreover, a striking morphological abnormality with the apparent absence of the pituitary stalk and an ectopic posterior pituitary lobe was detected in 34 of the patients (59%). This pituitary stalk abnormality was detected in 95% of the MPHD patients and in 39% of the IGHD patients. All but one of the patients with a normal pituitary stalk had IGHD. Endocrine evaluation showed no correlation with MRI data: in particular patients with an apparent anatomical interruption of the hypothalamic-pituitary axis showed a variety of patterns of hormonal responses. In conclusion, our study shows a high frequency of hypothalamic-pituitary anomalies in patients with GH deficiency, particularly related with MPHD. However, further studies are needed to improve our understanding of the relationship between MRI and endocrine data.     

G protein-coupled receptor systems and their lipid environment in health disorders during aging

Cells, tissues and organs undergo phenotypic changes and deteriorate as they age. Cell growth arrest and hyporesponsiveness to extrinsic stimuli are all hallmarks of senescent cells. Most such external stimuli received by a cell are processed by two different cell membrane systems: receptor tyrosine kinases (RTKs) and G protein-coupled receptors (GPCRs). GPCRs form the largest gene family in the human genome and they are involved in most relevant physiological functions. Given the changes observed in the expression and activity of GPCRs during aging, it is possible that these receptors are directly involved in aging and certain age-related pathologies. On the other hand, both GPCRs and G proteins are associated with the plasma membrane and since lipid-protein interactions regulate their activity, they can both be considered to be sensitive to the lipid environment. Changes in membrane lipid composition and structure have been described in aged cells and furthermore, these membrane changes have been associated with alterations in GPCR mediated signaling in some of the main health disorders in elderly subjects. Although senescence could be considered a physiologic process, not all aging humans develop the same health disorders. Here, we review the involvement of GPCRs and their lipid environment in the development of the major human pathologies associated with aging such as cancer, neurodegenerative disorders and cardiovascular pathologies.     

A novel 500,000 Da, linear, single chain extracellular protein synthesized by several childhood tumors

A high molecular weight extracellular protein has been purified from cell culture medium of Ewing's sarcoma cell lines, by high performance liquid chromatography and electroelution from SDS-PAGE electrophoresis. This protein has an apparent molecular mass of about 500,000 Da on SDS-PAGE. Immunoprecipitation studies with several extracellular matrix glycoproteins (laminin, fibronectin) specific antisera indicate it is a separate protein. Reduction of disulphide bonds with 2-ME or DTT fails to significantly alter its migration on SDS-PAGE gels, other than a slight apparent increase in molecular mass, indicating an apparent single polypeptide chain structure. The slightly greater mobility observed in unreduced gels suggests one or more regions of intrachain disulfide bonding. It is sensitive to pepsin and trypsin, but resistant to bacterial collagenase indicating that it does not contain collagenous domains. Metabolic labelling with 3H-proline, 3H-leucine, and 35S-methionine indicate that this protein is proline-poor, but leucine, and especially methionine, rich. Sodium 35S-sulfate incorporation is totally negative and treatment with glycosaminoglycan degrading enzymes has no effect on the mobility of the protein on gels, unlike typical proteoglycans. This protein appears by rotary shadowing electron microscopy as a long, thin, filamentous molecule at least 500 nm (0.5 um) in length. The tissue localization and function are unknown at this time, but are under active investigation.     

Some Nutritional Characteristics of a Naturally Occurring Alga (Microcystis sp.) in a Guatemalan Lake

The nutritional characteristics of an alga (Microcystis sp.) that occurs naturally in a Guatemalan lake were determined. The sun-dried material proved to have a high protein content (55.6%) and to be a possible good source of calcium and phosphorus (1, 169.1 and 633.4 mg/100 mg, respectively). Amino acid analysis showed that total sulfur amino acids were the most deficient ones, giving a protein score of 42 to the material. The in vitro protein digestibility of the material was 69.5%. Biological trials demonstrated that when the material was offered as the only protein source, very low consumption and a high mortality rate were obtained whether or not the diet was supplemented with 0.4% dl-methionine. However, when the material supplied 25% of the total protein of a corn-algae diet, the protein quality of the cereal was significantly improved (P < 0.05).     

Solid-State Fermentation: an Alternative to Improve the Nutritive Value of Coffee Pulp

Coffee pulp was subjected to a solid-state fermentation process, using Aspergillus niger. The initial moisture content of the pulp, as well as the fermentation time and temperature, had a significant effect on the increase in total amino acid content of the material. The increase in total amino acids showed a significant correlation with the dry matter recovered (r = −0.98) and the increase in pH during the process (r = 0.98). With a moisture content of 80%, a pH of 3.5, a temperature of 35°C, and an aeration of 8 liters/min per kg as fermentation conditions, it was found that the maximum concentration of total amino acids was attained after 43 h. The fermented product had a higher total amino acid content and a lower cell wall constituent value (primarily cellulose and hemicellulose) than the original pulp. A growing chicken's ration containing 10% of the fermented product had a feed efficiency (2.14) similar to that of the standard ration (2.19) and was significantly better than that of the diet containing 10% of the original pulp (2.53). The difference observed in feed intake and weight gain between the standard diet and that with 10% of the fermented product is considered to be due to palatability factors which should be studied further.     

Prune homolog 2 with BCH domain (PRUNE2) gene expression is associated with feed efficiency-related traits in Nelore steers

Mammalian Genome - Animal feeding is a critical factor in increasing producer profitability. Improving feed efficiency can help reduce feeding costs and reduce the environmental impact of beef...