PROPS sensor induction

Adam Cohen’s PROPS sensor is a fluorescent indicator of the proton-motive force. Here’s an adaption of the protocol to induce expression of the PROPS protein (which is on the pBAD promoter).

Materials

• 20 mM all-trans retinal stock solution in ethanol
• 10% w/v arabinose stock
• 1X M9 salt with 0.4% glucose, pH 7.0
• LB

Procedure

1. Grow strain in 50 mL of LB at 33C until you reach an OD = 0.3-0.4
2. Add arabinose (100 uL of stock, i.e. to 0.02%) and all-trans retinal (12.5 uL of stock, i.e. to 5 uM)
3. Grow in dark for 3.5 hours at 33C
4. Harvest cells and wash in 30 mL of the M9 medium
5. Resuspend cells in 5 mL M9 medium and store at 4C for later use (can store up to 2 weeks)