Quorum Sensing

110

a

b

c

100

90

80

70

60

50

40

30

20

10

5.0 5.1

holo-ACP

C4-ACP

SAM

MTA

5.2 5.3 5.4 5.5 5.6

Minutes

mAU

1400

1200

1000

800

600

400

200

0

mAU

5.7 5.8 5.9 6.0 6.1

0.0 1.0 2.0 3.0

Minutes

4.0 5.0 6.0

Fig. 5HPLC assay. (a) Chromatogram for acylation half-reaction. The concentrations of C4-ACP, SAM, and RhlI
are, respectively, 20μM, 300μM, and 0.3μM. The chromatogram represents a snapshot of relative
proportions of acyl-ACP and holo-ACP assay component present in the assay mixture that was quenched
4 min after enzyme addition. (b) Chromatogram for lactonization half-reaction. The chromatogram is a 6-min
quenched reaction that contained 27μM C4-ACP, 300μM SAM, and 0.3μM RhlI enzyme. (c) Acylation and
lactonization chemical steps in AHL synthesis