SH3‐like motif‐containing C‐terminal domain of staphylococcal teichoic acid transporter suggests possible function

The negatively charged bacterial polysaccharides—wall teichoic acids (WTAs) are synthesized intracellularly and exported by a two‐component transporter, TagGH, comprising a transmembrane subunit TagG and an ATPase subunit TagH. We determined the crystal structure of the C‐terminal domain of TagH (TagH‐C) to investigate its function. The structure shows an N‐terminal SH3‐like subdomain wrapped by a C‐terminal subdomain with an anti‐parallel β‐sheet and an outer shell of α‐helices. A stretch of positively charged surface across the subdomain interface is flanked by two negatively charged regions, suggesting a potential binding site for negatively charged polymers, such as WTAs or acidic peptide chains. Proteins 2016; 84:1328–1332. © 2016 Wiley Periodicals, Inc.     

In Vivo Neurochemical Characterization of Developing Guinea Pigs and the Effect of Chronic Fetal Hypoxia

Neurochemical Research - The guinea pig is a frequently used animal model for human pregnancy complications, such as oxygen deprivation or hypoxia, which result in altered brain development. To...     

New late gene, dar, involved in the replication of bacteriophage T4 DNA. III. DNA replicative intermediates of T4 dar and a gene 59 mutant suppressed by dar.

A mutation in the dar gene of phage T4 restored the arrested DNA synthesis caused by the gene 59 mutation. We have studied the DNA replicative intermediates in cells infected with a dar mutant and a dar-amC5 (gene 59) mutant by velocity sedimentation in neutral and alkaline sucrose gradients. In T4 dar-infected cells, compared to the wild type, three kinds of abnormalities were observed in DNA replication (i) There were unusually rapidly sedimenting intermediates (800S). (ii) When centrifuged in alkaline gradients, there was less single-stranded DNA exceeding 1 phage unit. (iii) The rate of repair of DNA intermediates was slower. It has been proposed by others that the 200S DNA replicative intermediates are required for DNA packaging, but our results showed that the 800S DNA of dar does not have to be converted into the 200S form to undergo conversion to mature viral DNA. Therefore, 200S DNA may not be an obligatory intermediate for mature viral DNA formation. In amC5 (gene 59)-infected cells, the DNA was completely converted 2 to 3 min after intiation of replication to the biologically inactive 63S DNA, and DNA synthesis was concomitantly arrested. However, in dar-am-C5 (gene 59)-infected cells, the formation of abnormal 63S DNA did not occur and 200S DNA appeared instead. An endonucleolytic activity, normally associated with the cell membrane and capable of making double-stranded cuts, was found in the cytoplasm of T4 dar-infected cells. Because the total activity of this endonuclease is the same for both wild-type T4D and the dar mutant, it seems unlikely that the dar protein has endonucleolytic activity itself. However, the finding does explain the abnormal sedimentation of dar DNA intermediates (800S) as well as the proposed suppression mechanism of the gene 59 mutation.     

The mod A mutant of Dictyostelium discoideum is missing the alpha 1,3-glucosidase involved in asparagine-linked oligosaccharide processing

The recessive mutation, mod A, in the Dictyostelium discoideum strain M31 results in an alteration in the post-translational modification of lysosomal enzymes. We now report studies which indicate that mod A is deficient in glucosidase II, an enzyme which is involved in the processing of asparagine-linked oligosaccharides. [2-3H]Mannose-labeled glycopeptides were prepared from three purified mod A lysosomal enzymes and compared to the equivalent glycopeptides from parental enzymes. The mod A glycopeptides were deficient in high mannose oligosaccharides containing two phosphomannosyl residues and accumulated oligosaccharides with one phosphomannosyl residue. The phosphate was present in the form of an acid-stable phosphodiester in both instances. There was also an increase in the amount of nonphosphorylated high mannose oligosaccharides mod A and these were larger than the corresponding material from the parental enzymes. In addition, the nonphosphorylated oligosaccharides were only partially degraded by alpha-mannosidase, indicating the presence of a blocking moiety. In vitro enzyme assays demonstrated that the mod A cells cannot remove the inner 1 leads to 3-linked glucose from a glucosylated high mannose oligosaccharide. The cells are also deficient in membrane-bound neutral p-nitrophenyl-alpha-D-glucosidase activity. This activity has been attributed to glucosidase II in other systems. Removal of the outer 1 leads to 2-linked glucose from Glc3Man9Glc-NAc2 is normal, demonstrating the presence of glucosidase I activity. We conclude from these data that M31 cells are deficient in glucosidase II, the enzyme which removes the two inner glucose residues from the glucosylated oligosaccharides of newly glycosylated proteins. This defect can explain the mod A phenotype and is proposed to be the primary genetic defect in these cells.     

Dietary citrate supplementation enhances longevity,metabolic health,and memory performance through promoting ketogenesis

Citrate is an essential substrate for energy metabolism that plays critical roles in regulating cell growth and survival. However, the action of citrate in regulating metabolism, cognition, and aging at the organismal level remains poorly understood. Here, we report that dietary supplementation with citrate significantly reduces energy status and extends lifespan in Drosophila melanogaster. Our genetic studies in fruit flies implicate a molecular mechanism associated with AMP‐activated protein kinase (AMPK), target of rapamycin (TOR), and ketogenesis. Mice fed a high‐fat diet that supplemented with citrate or the ketone body β‐hydroxybutyrate (βOHB) also display improved metabolic health and memory. These results suggest that dietary citrate supplementation may prove to be a useful intervention in the future treatment of age‐related dysfunction.     

Trace element concentration and arsenic speciation in the well water of a Taiwan area with endemic Blackfoot disease

Blackfoot disease is a peripheral vascular disease resulting in gangrene of the lower extremities. Although extensive epidemiological study has implicated high arsenic content in artesian well water in the endemic area, there is more to learn about the etiology of the disease. In this study, effort is paid on multielement determination and arsenic speciation in order to find out whether the trace element concentration pattern in well water in the Blackfoot disease endemic area is different from those of two control areas. Experimental results indicate that the concentrations of Fe, P, Na, and Ba in well water in the Blackfoot disease endemic area are found to be significantly higher than those of the controls, but they are still below the drinking water standard. The total arsenic in well water in the endemic area (671±149 ppb) is much higher than that of one normal control area of Hsin-Chu (<0.7 ppb), but is a similar level as that of other control areas of I-Lan (653±71 ppb) where no Blackfoot disease has ever been found. It was also found that the insoluble arsenic in the endemic area (21.9 ppb) is much higher than that in two control areas (≤1.8 ppb), and the concentration ratio between As(III) and As(V) species in the endemic area (2.6) is much lower than that in one of the control areas, where the total arsenic is also high (14.7). The possible connection of Blackfoot disease with trace elements, arsenic species, and possibly other as yet undefined environmental factors in the artesian well water, is discussed.     

Annonacin,a mono-tetrahydrofuran acetogenin,arrests cancer cells at the G1 phase and causes cytotoxicity in a Bax- and caspase-3-related pathway

Annonaceous acetogenins are a group of potential anti-neoplastic agents isolated from Annonaceae plants. In this study, we purified annonacin, a cytotoxic mono-tetrahydrofuran acetogenin, from the seeds of Annona reticulata and analyzed its biological effects. Herein, we have shown that annonacin caused significant cell death in various cancer cell lines. T24 bladder cancer cells at the S phase were more vulnerable to the cytotoxicity of annonacin. Furthermore, annonacin activated p21 in a p53-independent manner and arrested T24 cells at the G1 phase. It also induced Bax expression, enhanced caspase-3 activity, and caused apoptotic cell death in T24 cells. In summary, these results suggest that annonacin is potentially a promising anti-cancer compound.