TABLE 2.

Erythromycin and ABT-773 ribosome binding kinetics^a

Drug	Initial uptake (pmol/109 CFU/min)	k1 (M−1 min−1)	k−1 (min−1)	Kd (M)
Erythromycin	10.8	5.28 × 105	0.0215	4.1 × 10−8
ABT-773	37.4	2.62 × 106	0.0016	6.1 × 10−10
Ratiob	0.3	0.2	13	67

^aAnalysis based on cellular drug influx and efflux rates as described in Materials and Methods. Kinetic constants: k₁, forward rate constant; k₋₁, reverse rate constant; K_d, dissociation constant = k₋₁/k₁. The strain used was S. pneumoniae 2486. 

^bErythromycin/ABT-773.