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. 1998 Feb;180(3):449–456. doi: 10.1128/jb.180.3.449-456.1998

TABLE 1.

Competitive inhibition analysis with cold pheromones and inhibitors

Pheromone or inhibitor Sequence Inhibition of [3H]cPD1 binding (IC50 [nM])a to:
cPD1 activitye (nM)
TraCb Donor spheroplastc GST-TraAd
cPD1 H-Phe-Leu-Val-Met-Phe-Leu-Ser-Gly-OH 34.2 1.49 0.50 0.1
iPD1 H-Ala-Leu-Ile-Leu-Thr-Leu-Val-Ser-OH 78.5 0.45 0.33 >350
cAD1 H-Leu-Phe-Ser-Leu-Val-Leu-Ala-Gly-OH >1,000 >1,000 >1,000 >350
iAD1 H-Leu-Phe-Val-Val-Thr-Leu-Val-Gly-OH >1,000 >1,000 >1,000 >350
cCF10 H-Leu-Val-Thr-Leu-Val-Phe-Val-OH 126 >1,000 >1,000 >1,000
iCF10 H-Ala-Ile-Thr-Leu-Ile-Phe-Ile-OH 100 >1,000 >1,000 >350
cAM373 H-Ala-Ile-Phe-Ile-Leu-Ala-Ser-OH >1,000 >1,000 >1,000 >350
iAM373 H-Ser-Ile-Phe-Thr-Leu-Val-Ala-OH >1,000 >1,000 >1,000 >350
cOB1 H-Val-Ala-Val-Leu-Val-Leu-Gly-Ala-OH >1,000 >1,000 >1,000 >350
iOB1 H-Ser-Leu-Thr-Leu-Ile-Leu-Ser-Ala-OH 16.5 >1,000 >1,000 >350
a

Concentrations of cold peptides that produce 50% inhibition of the specific binding (IC50) were estimated from the plots of [3H]cPD1 binding. The specific binding was calculated by subtraction of the nonspecific binding determined in the presence of 1 μM cold cPD1 from the maximum binding. 

b

Binding to TraC was assayed with TraC-expressing cells (intact cells of OG1X carrying pDLES23) and 0.5 nM [3H]cPD1. 

c

Binding to donor spheroplasts was assayed with spheroplasts of OG1X carrying pAM351 and 0.5 nM [3H]cPD1. 

d

Binding to GST-TraA was assayed with 20 nM GST-TraA and 0.2 nM [3H]cPD1. 

e

cPD1 activity represents the minimum concentration inducing cell clumping of a pPD1 donor strain (39-5Sα) in a microtiter bioassay (40).