Table 1.
Comparison of features of cAMP-signaling in three bacteria
| Bacterium | M. tuberculosis | E. coli | P. putida |
|---|---|---|---|
| Niche | Lung macrophage | Mammalian intestine | Soil |
| Number of adenylyl cyclases | 16 | 1 | 2 |
| Intracellular cAMP concentrations | High | Moderate | Low |
| CRP | Rv3676 | CRP | PP_0424 |
| cAMP–CRP interactions | Independent binding | Cooperative binding | Independent binding |
| KD for cAMP | ∼60 μm | ∼13–16 μm | ∼23 nm |
| Motif for cAMP interactiona | E…TS…R…TN | E…RS…R…TS | E…RS…R…TT |
| Number of phosphodiesterases | 1 | 1 | 1 |
| Number of chromosomal binding sitesb | >70 | >378 | >30 |
a
Amino acids involved in direct interaction with cAMP in E. coli CRP as single letter code with dots (…) representing intervening regions of various lengths. The amino acid at the position equivalent to Ser-128 in E. coli CRP that makes a cross-subunit contact with cAMP is shown in bold font.
b
The binding site numbers represent: matches to the Rv3676 consensus sequence identified by Rickman et al. [28] in the M. tuberculosis H37Rv genome sequence; E. coli CRP-binding sites suggested by Shimada et al. [15•] following genomic SELEX analysis; and a minimum value based on interrogation of the P. putida KT2440 genome sequence by the E. coli CRP-binding site consensus [30•].