A systems biology approach reveals major metabolic changes in the thermoacidophilic archaeon Sulfolobus solfataricus in response to the carbon source L-fucose versus D-glucose

Archaea are characterised by a complex metabolism with many unique enzymes that differ from their bacterial and eukaryotic counterparts. The thermoacidophilic archaeon Sulfolobus solfataricus is known for its metabolic versatility and is able to utilize a great variety of different carbon sources. However, the underlying degradation pathways and their regulation are often unknown. In this work, the growth on different carbon sources was analysed, using an integrated systems biology approach. The comparison of growth on L-fucose and D-glucose allows first insights into the genome-wide changes in response to the two carbon sources and revealed a new pathway for L-fucose degradation in S. solfataricus. During growth on L-fucose major changes in the central carbon metabolic network, as well as an increased activity of the glyoxylate bypass and the 3-hydroxypropionate/4-hydroxybutyrate cycle were observed. Within the newly discovered pathway for L-fucose degradation the following key reactions were identified: (i) L-fucose oxidation to L-fuconate via a dehydrogenase, (ii) dehydration to 2-keto-3-deoxy-L-fuconate via dehydratase, (iii) 2-keto-3-deoxy-L-fuconate cleavage to pyruvate and L-lactaldehyde via aldolase and (iv) L-lactaldehyde conversion to L-lactate via aldehyde dehydrogenase. This pathway as well as L-fucose transport shows interesting overlaps to the D-arabinose pathway, representing another example for pathway promiscuity in Sulfolobus species.

Up-regulation of BOB.1/OBF.1 expression in normal germinal center B cells and germinal center-derived lymphomas

The BOB.1/OBF.1/OCAB.1 protein is a lymphocyte-specific transcriptional coactivator. It interacts with the Oct1 and Oct2 transcription factors and contributes to the transcriptional activity of octamer motifs. The analysis of established B cell lines had suggested that BOB.1/OBF.1 is constitutively expressed at all stages of B cell development. Here we show that expression of BOB. 1/OBF.1 is regulated within the B cell lineage. Specifically, germinal center B cells show highly increased BOB.1/OBF.1 levels. We can induce the up-regulation by stimulating primary splenic B cells, eg, by triggering CD40 signaling in the presence of interleukin-4. Expression of BOB.1/OBF.1 is detectable but reduced in spleens from mice unable to undergo the germinal center reaction due to mutations in the TNF receptor p55 or lymphotoxin beta (LTbeta) receptor genes. Furthermore, we demonstrate that BOB.1/OBF.1 expression is highly regulated in human B cell lymphomas. Whereas lymphomas representing pre- and postfollicular B cell developmental stages are negative for BOB.1/OBF.1, high-level expression of BOB.1/OBF.1 is characteristic of germinal center-derived tumors. In these tumors BOB.1/OBF.1 is typically coexpressed with high levels of Bcl6. These results imply that overexpression of BOB.1/OBF.1, like overexpression of Bcl6, might play a role in the pathogenesis of germinal center-derived B cell lymphomas. Furthermore, overexpression of BOB.1/OBF.1 represents a characteristic feature of these tumors that is useful in their identification.

Development of highly selective SH3 binding peptides for Crk and CRKL which disrupt Crk-complexes with DOCK180, SoS and C3G

Many Src Homology 3 (SH3) domains function as molecular adhesives in intracellular signal transduction. Based on previous ultrastructural studies, short motifs which bind to the first SH3 domains of the adapters Crk and CRKL were selectively mutagenised to generate Crk/CRKL SH3-binding peptides of very high affinity and selectivity. Affinities were increased up to 20-fold compared to the best wildtype sequences, while the selectivity against a similar SH3 domain [Grb2SH3(N)] was not only retained, but sometimes increased. Blot techniques with GST-fusion peptides and in solution precipitation assays with biotinylated high affinity Crk binding peptides (HACBPs) were subsequently used to analyse the binding of these sequences to a large panel of SH3 domain-containing fusion proteins. Only those proteins which contained the CrkSH3(1) or CRKLSH3(1) domains bound efficiently to the HACBPs. A GST-HACBP fusion protein precipitated Crk and CRKL proteins out of 35S-labelled and unlabelled cell lysates. Very little binding of other cellular proteins to HACBP was detectable, indicative of a great preference for Crk and CRKL when compared to the wide variety of other endogenous cellular proteins. Moreover, HACBP disrupted in vitro preexisting Crk-complexes with DOCK180 and the exchange factors SoS and C3G, which are known targets of Crk adapters, in a concentration dependent manner. HACBP-based molecules should therefore be useful as highly selective inhibitors of intracellular signalling processes involving Crk and CRKL.

Characterization of antibodies against human N-terminal parathyroid hormone by epitope mapping

Two polyclonal antisera from goat and mouse and two monoclonal antibodies against human parathyroid hormone (1-34) were characterised by epitope mapping. Hexapeptides were synthesized on polystyrene pins, the sequences of which overlapped and represented the entire sequence of hPTH(1-34). Binding of antibodies to these hexapeptides was determined and antigenic determinants thus characterized. At least one predominant binding sequence was detected in the region of hPTH(7-14).