FIGURE 4.

Binding of the fluorescent penicillin derivative Bocillin FL to PBPs recovered from RUSA130 and exposed to 12.5 μg/ml ECg. This strain produces a truncated form of PBP2 and enables the detection of PBP2a, which migrates in gels in an identical fashion to native PBP2. After incubation with ECg, the samples were labeled with 25 μm Bocillin FL and separated by 10% SDS-PAGE, and the proteins were detected by fluorography. −, no ECg. Truncated PBP2 has very low affinity for β-lactam agents (29, 48) and does not bind sufficient Bocillin FL for visualization on the gel.