FIG. 3.

Testing the binding specificity of the cell extract protein to SRSR-2p. SRSR-2p was ²³P end labeled and a band shift binding assay was performed in the presence of unlabeled SRSR-2p or control DNA amplified from another region of pNOB8 (see text). We used 1.4 μg of cell extract protein from Sulfolobus sp. strain NOB8H2 (lanes 2 to 9) and 1 μg of cell extract protein from conjugated S. solfataricus P2 (lanes 10 to 17). The approximate molar ratios of unlabeled SRSR-2p to ³²P-end-labeled SRSR-2p (3 ng) are given above the lane. “No comp.” indicates that no competing DNA was added.