β-Glucanase expression by Ruminococcus flavefaciens FD-1

Abstract Ruminococcus flavefaciens has been hypothesized to produce cellulase constitutively. We have studied the effect of carbon source, either cellobiose or cellulose, on the production of cellulase in batch cultures of R. flavefaciens FD-1. Total CMCase and ¹⁴C-cellulase activity was approximately 2-fold higher in cellobiose grown cells than in cellulose grown cells, whereas p-nitrophenyl-β- d -cellobiosidase (PNPCase) activity was not affected by culture conditions. The addition of cellulose to cells growing on cellobiose did not alter the amount or rate of PNPCase and ¹⁴C-cellulase production. Northern blot analysis of mRNAs produced by R. flavefaciens FD-1 grown using either cellobiose or cellulose as the substrate indicated that two of the four β-glucanase genes cloned from R. flavefaciens FD-1 were only expressed in cells grown with cellulose as the substrate. Although the adherence of cells and cellulase enzyme to native cellulose can complicate interpretations of these data, the results indicate that cellulase synthesis by R. flavefaciens is differentially regulated by carbon source.     

Degree of polymerization and polydispersity of xylan from the cell wall of the green seaweed Penicillus dumetosus

Xylan was extracted from the cell wall of green seaweed penicillus domutosus using a very mild procedure. Xylan dinitrate samples were prepared and their degrees of polymerization found to depend markedly on temperature, of nitration, the best compromise between yield and degradation being at about ?20°C. Two samples, one obtained under optimum conditions and one highly degraded, were investigated in detail by using light-scattering, osmometry, gel-permeation chromatography, and viscosity techniques. The results show that there are xylan chains present, in the cell wall having degrees of polymerization above 10,000. This figure is much higher than those previously found for other similar xylans. The light-scattering results show that the xylan dinitrate molecule is much smaller than the molecules of the trinitrates of other structural polysaccharides (cellulose and mannan) for the same degree of polymerization. The effective bond length b is 16 Å, assuming a linear chain.     

Negative Regulation of CARD11 Signaling and Lymphoma Cell Survival by the E3 Ubiquitin Ligase RNF181

NF-κB activation downstream of antigen receptor engagement is a highly regulated event required for lymphocyte activation during the adaptive immune response. The pathway is often dysregulated in lymphoma, leading to constitutive NF-κB activity that supports the aberrant proliferation of transformed lymphocytes. To identify novel regulators of antigen receptor signaling to NF-κB, we developed bioluminescence resonance energy transfer-based interaction cloning (BRIC), a screening strategy that can detect protein-protein interactions in live mammalian cells in a high-throughput manner. Using this strategy, we identified the RING finger protein RNF181 as an interactor of CARD11, a key signaling scaffold in the antigen receptor pathway. We present evidence that RNF181 functions as an E3 ubiquitin ligase to inhibit antigen receptor signaling to NF-κB downstream of CARD11. The levels of the obligate signaling protein Bcl10 are reduced by RNF181 even prior to signaling, and Bcl10 can serve as a substrate for RNF181 E3 ligase activity in vitro. Furthermore, RNF181 limits the proliferation of human diffuse large B cell lymphoma cells that depend upon aberrant CARD11 signaling to NF-κB for growth and survival in culture. Our results define a new regulatory checkpoint that can modulate the output of CARD11 signaling to NF-κB in both normal and transformed lymphocytes.     

The Elementary Nervous System Revisited

Parker's theory of the origin of the nervous system is discussedalong with later interpretations. Attention today has shiftedfrom the cellular to the molecular level, and it has becomeclear that many of the molecules and mechanisms thought of astypically neuronal have homologs or counterparts in non-nervouscells and unicellular organisms. This applies to signallingchemicals, receptors, second messenger systems and ion channels,and also to the production of electrical events. Parker's viewof sponges as a group lacking nerves but possessing independenteffectors is still acceptable, but some sponges (and also higheranimals) employ non-nervous signalling pathways to coordinatetheir effectors. Thus, nerves are not always necessary for coordinatedbehavior. Cnidarians like hydra have seemingly simple, two-dimensionalnervous systems with little or no centralization, but even suchsystems can be surprisingly complex, and the more advanced cnidariansshow neurophysiological specializations as sophisticated asthose of many higher invertebrates. Examples of ingenious cnidariansolutions to behavioral problems are given. No existing animalshave ‘elementary’ nervous systems if that term impliesthe existence of crude or inefficient functional adaptations     

Structural investigation of Klebsiella serotype K70 polysaccharide

By using the techniques of methylation analysis, uronic acid degradation, partial hydrolysis, and periodate oxidation, the structure of the capsular polysaccharide from Klebsiella serotype K70 has been investigated. Nuclear magnetic resonance was used extensively to characterize fragments obtained as a result of the various degradation procedures. The existence of a linear, hexasaccharide repeating unit having a 1-carboxyethylidene group attached to a 2-linked α-l-rhamnosyl residue in every second repeating unit has been demonstrated.