Xanosporic acid,an intermediate in bacterial degradation of the fungal phototoxin cercosporin

The red fungal perylenequinone phototoxin cercosporin is oxidized by Xanthomonas campestris pv zinniae to a non-toxic, unstable green metabolite xanosporic acid, identified via its lactone as 1,12-bis(2'R-hydroxypropyl)-4,9-dihydroxy-6,7-methylenedioxy-11-methoxy-3-oxaperylen-10H-10-one-2-carboxylic acid. Xanosporolactone was isolated in approximately 2:1 ratio of M:P atropisomers.     

Distribution of SERCA isoforms in human intrafusal fibers

The sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA) is a membrane protein that plays a crucial role in muscle relaxation by transporting cytosolic Ca²⁺ into the lumen of the sarco/endoplasmic reticulum. In this study, the presence of SERCA1 and SERCA2 was investigated in human intrafusal fibers by immunocytochemistry. Nuclear bag₁ fibers contained both SERCA1 and SERCA2 isoforms, with predominant staining seen with SERCA2 in the A and B regions. Most nuclear bag₂ fibers also contained SERCA1 and SERCA2 isoforms and their coexistence frequently occurred in the A region. SERCA1 was present whereas SERCA2 was generally absent in the nuclear chain fibers. The staining intensity seen with the SERCA1 monoclonal antibody varied in the order of chain>bag₁>bag₂. The expression of SERCA1 isoform was found to correlate with the presence of fast myosin heavy chain (MyHC) isoform in nuclear chain fibers, whereas for nuclear bag fibers there was no such apparent correlation between patterns of expression of SERCA and MyHC isoforms. The phenotype revealed for the human bag fibers was very sophisticated and adapted to attain a very wide range of contraction and relaxation velocities.     

Modulation of granulomatous hypersensitivity against Schistosoma mansoni eggs in mice vaccinated with culture-derived macrophages loaded with PIII

Granuloma modulation induced by antigen is an attractive model for vaccination studies of experimental schistosomiasis to test the effect of anti-pathology vaccine. We describe here an immunization procedure with culture derived macrophages-pulsed PIII, a known anionic antigen purified from S. mansoni adult worm, involved in the inhibition of granulomatous response to eggs. For our studies, peritoneal or spleen macrophages cultured over 15 days were loaded with PIII. Both macrophage sub-populations were capable to efficiently take up and subsequently present PIII to lymphocytes as evidenced by immunofluorescence assay. The vaccination of mice with intravenous injection of PIII-loaded macrophages potently induced antigen-specific immune response to S. mansoni antigens as determined by cell proliferation assay. This immunization procedure of mice caused significant decrease in hepatic granuloma formation and in vitro granuloma reaction to S. mansoni antigens coupled to polyacrylamide beads (PB-SEA, PB-SWAP or PB-PIII). Assessment of in vitro granuloma supernatant of spleen cells from PIII-loaded macrophages vaccinated mice revealed significant amounts of Th1-cytokines IFN-gamma and IL-2 compared to control cells. Collectively, our results indicate that culture derived-macrophages provided a valuable research tool to investigate aspects of immune response that promote modulation of granulomatous hypersensitivity to S. mansoni eggs in mice.     

Effect of ethylene on enzymatic activities involved in the browning of Hevea brasiliensis callus

Browning, which is of varying intensity depending on species, develops in Hevea brasiliensis callus in vitro and can affect somatic embryogenesis. Endogenous ethylene appears to be involved since application of aminocyclopropane carboxylic acid (ACC) strongly enhances this browning. At the same time, peroxidases (EC 1.11.1.7), bonded polyphenol oxidase (EC 1.10.3.1) and NADH-quinone reductase (EC 1.6.99.5) are enhanced by ACC whereas superoxide dismutase (SOD: EC 1.15.1.1) and ascorbate peroxidase (EC 1.11.1.11) are decreased. In contrast, application of aminoacetic acid (AOA) causes spectacular decreases in bound and soluble polyphenol oxidase, peroxidase and NADH-quinone reductase activities whereas SOD and ascorbate peroxidase activities increase. Enzymatic activities in the control callus present a medium value, probably due to a considerable ethylene production in the culture medium. After 47 days culture. the initial catalase activity (EC 1.11.1.6) in the explants had disappeared completely. In contrast, after only 22 days, the silver nitrate and especially AOA treatments promoted considerable activities of catalase. The beneficial effect of the inhibitors of ethylene synthesis was reflected in the enhanced formation of embryogenic tissue, which varied from 1% (control or ACC) to 34% (AOA treatment).     

The tetrameric molecule of conventional kinesin contains identical light chains

Conventional kinesin is a multifunctional motor protein that transports numerous organelles along microtubules. The specificity of kinesin-cargo binding is thought to depend on the type(s) of light chains that a kinesin molecule contains. We have shown previously that different isoforms of kinesin light chains are associated with different types of cargo, mitochondria and membranes of the Golgi complex. Here, we provide evidence that the two light chains present within each kinesin molecule are always of the same type. Further, we demonstrate that kinesin heavy chains interact with nascent light-chain polypeptides on ribosomes. These data suggest that incorporation of the two identical light chains into a single kinesin molecule most likely occurs cotranslationally.     

Role of rpoS in the regulation of glyoxalase III in Escherichia coli

Methylglyoxal is an endogenous electrophile produced in Escherichia coli by the enzyme methylglyoxal synthase to limit the accumulation of phosphorylated sugars. In enteric bacteria methylglyoxal is detoxified by the glutathione-dependent glyoxalase I/II system, by glyoxalase III, and by aldehyde reductase and alcohol dehydrogenase. Here we demonstrate that glyoxalase III is a stationary-phase enzyme. Its activity reached a maximum at the entry into the stationary phase and remained high for at least 20 h. An rpoS- mutant displayed normal glyoxalase I and II activities but was unable to induce glyoxalase III in stationary phase. It thus appears that glyoxalase III is regulated by rpoS and might be important for survival of non-growing E. coli cultures.