The Escherichia coli GcvB sRNA Uses Genetic Redundancy to Control cycA Expression
Figure 1
(a) The gcvA/gcvB promoter region and gcvB gene. Promoter −35 and −10 elements are underlined for gcvA and overlined for gcvB [1, 15]. The GcvA-binding site is indicated by a line [16]. Inverted arrows show stem-loop sequences of putative transcription terminator t1 and terminator t2. A 13 base and a 10 base conserved sequence in gcvB homologs are designated Con-I and Con-II (green bars) [1, 3, 5]. Con-I is part of a larger G/T-rich domain (dashed line) essential for interaction of GcvB with most characterized target mRNAs [4, 5, 13]. Bases in GcvB complementary with cycA mRNA in the +73 to +82 region are in red and in the +124 to +161 region in blue. Changes in gcvB shown not to alter cycA-lacZ expression are below the sequence and are color coded [2]. Two independent changes isolated using pgcvB+142CA+159CC as template and that result in loss of GcvB repression of cycA-lacZ are boxed. (b) Comparison of GcvB from nt +124 to +166 with cycA mRNA. (c) Comparison of GcvB from nt +60 to +96 with cycA mRNA. For (b) and (c), complementarity is indicated with lines and GU bps with dots. Changes in gcvB are shown below the sequences, and changes in cycA are shown above the sequences and are color coded (see text for details).
