Table 1.

In vivo effects of mutations on the autoregulation of a translational fusion rpsO-lacZ

Pseudoknot		β-galactosidase units in the presence of plasmids		Repression ratio
Base pair	Mutation	pBR322 (control)	pBP111 (+ rpsO)
	Wild type	869  ±  50	39  ±  3	22
G-48 C-37	C·C	3,297  ±  264	2,768  ±  166	1.2
G-48 C-37	C·G	2,069  ±  69	184  ±  14	14
U-49 G-36	C·G	3,873  ±  160	3,460  ±  132	1.1
U-49 G-36	A·G	1,927  ±  199	1,894  ±  193	1.0
U-49 G-36	G·G	3,399  ±  198	1,418  ±  84	2.5
U-49 G-36	U·A	2,467  ±  56	2,322  ±  155	1.1
U-49 G-36	C·A	3,188  ±  81	2,641  ±  197	1.2
U-49 G-36	A·C	3,967  ±  565	3,293  ±  528	1.2
U-49 G-36	G·U	4,387  ±  119	3,131  ±  80	1.4
C-50 G-35	G·G	1,421  ±  94	1,392  ±  56	1.2
C-50 G-35	G·C	3,963  ±  66	3,131  ±  49	1.4
C-50 G-35	A·U	3,466  ±  281	2,994  ±  143	1.2
C-50 G-35	U·A	3,769  ±  468	2,947  ±  341	1.3
G-51 C-34	G·A	2,137  ±  68	188  ±  39	11
G-51 C-34	U·C	2,621  ±  88	1,689  ±  245	1.5
G-51 C-34	U·A	1,295  ±  42	98  ±  39	13

To analyze the expression of the ribosomal protein S15, a translational in frame fusion between rpsO, the gene encoding S15, and lacZ was used and the level of β-galactosidase (Miller units) measured in the presence of an overproduction of S15 in trans (pBP111) and in the absence (pBR322). The ratio between the two values (repression ratio) measures the efficiency of the regulation. The higher this value, the stronger the regulation. Conversely, when no control is present, this ratio decreases to 1.