g. the hexapeptide hydrazide 3, Fig. 1). The results obtained in assays with vanOxyB and balOxyB are summarized in Table 2. Intriguingly, all of the electron transfer proteins are able to effectively donate two electrons to vanOxyB during the catalytic cycle, using the hexapeptide–PCP

APO866 cost (1) as a substrate, with conversions to monocyclic product (3), under the standard conditions, ranging from 60 to over 90%. The heptapeptide–PCP (2, Fig. 1), however, is less efficiently converted into the corresponding monocyclic product, with conversions from 10% to 60% observed. It is important, however, to note that this heptapeptide substrate (2) is a mixture of inseparable diastereomers GSI-IX cell line (which arise during the synthesis of the substrate) differing in configuration at C(α) in residue-7. The results also suggest a more favorable interaction between vanOxyB

and spinFd or balFd-VII, than between vanOxyB and ecoFld or balFd-V. Similar findings were obtained in activity assays using balOxyB. In this case, however, the differences in substrate turnover achieved with the four electron transfer proteins, and between the hexa- and heptapeptide substrates, are more pronounced. Assays with balOxyB and ecoFld or balFd-V showed only a marginal turnover of hexapeptide (1) to a monocyclic product (3). However, with spinFd and especially with balFd-VII, significant cyclization of the substrate was observed (Table 2), with conversion of most hexapeptide to monocycle similar to that seen in assays with vanOxyB. However, the turnover of heptapeptide (2) was significantly lower, with the best result

being 15% conversion to a monocyclic product achieved with balFd-VII. These results suggest a higher discrimination between the hexa- and heptapeptides, with the hexapeptide being more strongly favored as a substrate by balOxyB. Finally, these findings also indicate degeneracy in the ability of various different Fds to support the catalytic activities of P450 coupling enzymes from different glycopeptide-producing organisms. This property may well make it difficult to assign a specific function to each of the individual Fds identified in the A. balhimycina genome, at least using in vitro assays. On the other hand, this flexibility should be an advantage in facilitating more detailed in vitro studies of these interesting cytochrome P450 cross-linking enzymes. The authors thank the Swiss National Science Foundation and the EU 6th framework program for supporting the project COMBIGTOP (LSHB-CT-2003-503491). “
“The existence of large number of a member of the Bacteroidetes in NaCl-saturated brines in saltern crystallizer ponds was first documented in 1999 based on fluorescence in situ hybridization studies. Isolation of the organism and its description as Salinibacter ruber followed soon.