Table 1.
Ciprofloxacin susceptibility of QnrC and QnrA1 mutants.
| Groups/clusters | Mutagenesis and codon alteration a | Position of mutation | Qnr protein | MIC (μg ml-1) |
|---|---|---|---|---|
| pHSG398 | - | - | 0.002 | |
| Control | pHS12 | wild type | QnrC | 0.125 |
| pMG252-1 | wild type | QnrA1 | 0.125 | |
| L38R(TTA→AGA) | i | QnrC | 0.003 | |
| L38A(TTA→GCA) | i | QnrC | 0.125 | |
| Hydrophobic interior of β-helix | L38F(CTG→TTC) | i | QnrA1 | 0.125 |
| F13S(TTC→TCC)c | i | QnrA1 | 0.008 | |
| C72Y(TGC→TAC) or A97Y(GCT→TAT) | i-2 | QnrC | 0.003 | |
| S116P (TCT→CCT) c | i+2 | QnrC | 0.002 | |
| Constraint effect of Pro to the backbone | S153P(TCT→CCT)c | i-1 | QnrC | 0.003 |
| L38P(CTG→CCG)c | i | QnrA1 | 0.004 | |
| C84S(TGT→TCT) | i | QnrC | 0.094 | |
| C84S(TGC→AGC) | i | QnrA1 | 0.064 | |
| Cys to Ser mutation | C31 S or C36 S or C57 S or C177 S (TGT→AGT); C26 S or C46 S or C72 S or C92 S or C122 S or C137S(TGC→AGC) |
i-2 | QnrA1 | 0.125 |
| C133S(TGC→AGC)or C168S(TGT→AGT) | i-1 | QnrA1 | 0.125 | |
| C115S(TGC→AGC)or C200S(TGT→AGT) | i+1 | QnrA1 | 0.125 | |
| Δ11-20 | N-terminus | QnrC | 0.003 | |
| Δ2-21 | N-terminus | QnrA1 | 0.002 | |
| Δ2-10 | N-terminus | QnrA1 | 0.003 | |
| Δ49-55 | G56 region | QnrC | 0.003 | |
| Fragment truncation b | Δ41-56, Δ51-56 | G56 region | QnrA1 | 0.003 |
| Δ77-96, Δ137-156 | β-helix backbone | QnrC | 0.003 | |
| Δ216-218 | C-terminus | QnrC | 0.064 | |
| Δ187-218 | C-terminus | QnrA1 | 0.003 | |
| Δ207-218 | C-terminus | QnrA1 | 0.004 | |
| D188V (GAC→GTC)c | i+1 | QnrA1 | 0.003 | |
| Others | M44T(ATG→ACG) | i+1 | QnrC | 0.125 |
| I216T (ATT→ACT) c | i+2 | QnrC | 0.125 | |
| E50A(GAA→GCC) or E50G (GAA→GGC) or E55A (GAA→GCT) or E55G(GAA→GGA) | i+2 | QnrA1 | 0.125 | |
a nucleotide substitution is in parentheses
b Δ2-21 indicates deletion of amino acids 2-21
c mutations were obtained by random mutagenesis and confirmed by site-directed mutagenesis