Table II. Residues involved in the MalT interaction patch as deduced by mutational screening of repressor-negative MalY mutants.
| Plasmid | β-galactosidase activitya |
|
|---|---|---|
| before inductionb | after inductionc | |
| Wild-type | 0.03 | 0.005 |
| Null (vector) | 2.17 | 2.68 |
| T83A | 1.29 | 0.03 |
| T83Id | 1.16 | 0.47 |
| A84T | 0.29 | unstable |
| A84V | 1.11 | 0.01 |
| C181Rd | 0.99 | 0.01 |
| C181T | 1.43 | 0.02 |
| C181T, T244Y | 0.26 | unstable |
| E185G | 1.16 | 0.02 |
| A188T | 0.92 | 0.002 |
| D189G | 0.58 | 0.001 |
| I215Td | 1.46 | 1.26 |
| S218R | 1.43 | 0.22 |
| N219D | 1.26 | 0.01 |
| A221Vd | 1.45 | 0.33 |
aSpecific β-galactosidase activity of the malK–lacZ fusion of strain EZ7 after growth overnight in minimal medium with glycerol as the carbon source. Specific activity is given in μmol substrate hydrolysed/min/mg protein.
bThe reduction of MalY-related repressor function is proportional to the value of β-galactosidase activity before induction with IPTG.
cInduction was with 100 μM IPTG.
dMutation that was obtained more than once.