Plasmid templates for analysis of the mechanism of
glnAp2 promoter activation by NtrC-dependent enhancer.
Strong and weak NtrC-binding sites are indicated by closed and open
boxes, respectively. Under our experimental conditions, only the strong
sites are occupied and contribute to the enhancer activity (11). The
pTH8 and pLR100 plasmids (3.6 and 3.3 kb in size, respectively) have
110-bp wild type (wt) enhancer–promoter spacing. The pLY10, pLY11, and
pLY12 plasmids (7.6, 7.4, and 7.4 kb in size, respectively) have 2.5
kb, 2.5 kb, and 2.3 kb enhancer–promoter distances (the
enhancer–promoter distances on the other side of the enhancer are
indicated in italics). pAN6 has no strong NtrC-binding sites. The
transcripts were terminated at the T7 terminator positioned at
different distances downstream of the promoter. The lengths of the
transcripts are indicated.