FIG. 7.

In vitro transcription assay revealing that XynR acts as a transcriptional activator of the xynABD transcript. A 780-bp PCR product containing 275 bp of sequence upstream of xynD and 505 bp of the xynD gene itself (primers IVT-F and IVT-R) was hybridized with P. bryantii B₁4 cell extract (lane 0) and different concentrations (10 and 20 μg/ml) of the recombinant XynR polypeptide (lanes 10 and 20). A nuclease protection assay revealed the presence of an undegraded 523-bp fragment of DNA that corresponds to the xynD coding sequence from the PCR product (505 bp) and the 16 bp upstream of this fragment that corresponds to the transcription initiation site (Fig. 5). Electrophoresis was carried out under denaturing conditions (1% agarose and 9% formaldehyde)