TABLE 1.
The summary of 18 constructed hybrid chemoreceptors, their chemoeffectors, and pH responses
| Locus tag | Name a | LBD type | Hybrid type b | Established chemoeffectors c | Newly characterized chemoeffectors d | pH response e | |
|---|---|---|---|---|---|---|---|
| pH 6 | pH 8 | ||||||
| PA1251 | 4HB | T1, T3 | — | — | |||
| PA1608 | PctP | 4HB | T1, T2 | Guanine, inosine, adenosine, hypoxanthine, adenine, and guanosine | R | A | |
| PA1646 | HBM | T1, T3 | — | — | |||
| PA2561 | CtpH (31, 32) | 4HB | T1, T3 | Inorganic phosphate | |||
| PA2573 | 4HB | T1 | — | — | |||
| PA2652 | CtpM (14) | sCache | T1, T2 | Malate, + | — | — | |
| PA2654 | TIpQ (9) | dCache | T1 | Histamine, + | 2-Phenylethylamine, tyramine | R | R |
| PA2788 | McpN (33) | PilJ | T1 | Nitrate | — | — | |
| PA2867 | Unknown | T1, T3 | — | — | |||
| PA2920 | 4HB | T1, T3 | — | — | |||
| PA4307 | PctC (34, 35) | dCache | T1, T2 (34) | γ-Aminobutyric acid (GABA), + | 5-Aminovalerate, methyl 4-aminobutyrate | A | R |
| PA4309 | PctA (35, 36) | dCache | T1, T2 (36) | L-alanine (L-Ala), + | L-ornithine (L-Orn) (37) f | A | R |
| PA4310 | PctB (35, 36) | dCache | T1, T2 (36) | L-glutamine (L-Gln), + | L-ornithine (L-Orn) (37) f | — | — |
| PA4520 | NIT | T1, T3 | |||||
| PA4633 | PctD (10) | dCache | T1, T2 (10) | Acetylcholine, + | — | — | |
| PA4844 | CtpL (31, 32) | HBM | T1 | Inorganic phosphate | — | — | |
| PA4915 | 4HB | T1 | 2-Phenylethylamine | — | — | ||
| PA5072 | McpK (13) | HBM | T1, T3 | α-Ketoglutarate, + | — | — | |
Ligand specificities of respective chemoreceptors have been characterized in indicated publications.
T1, type 1 is a hybrid chemoreceptor with a fusion site within TM2; T2: type 2 has a fusion site at the end of the HAMP domain; T3, type 3 has the same fusion site as type 1 but contains in addition a random linker of five amino acids. Hybrids that responds to D-glucose are underlined, and the nonresponsive hybrids are not underlined. For functional hybrid chemoreceptors that have been described previously, the references are provided in brackets.
Previously established ligands, with “+” indicating that the hybrid receptor was able to mediate a FRET response to this ligand.
Newly characterized chemoeffectors that showed positive results in FRET and/or ITC assays.
pH responses of hybrids, measured by changing buffer pH from 7 to either 6 or 8 using FRET assay. “A,” attractant response; “R,” repellent response; “—,” no response.
This study showed that PctA and PctB are required for chemotaxis of P. aeruginosa to L-ornithine, but no further characterization of L-ornithine binding to PctA or PctB was performed.