Figure 4.

Cadaverine Is a Bacterial Ligand for a Specific Histamine Receptor

(A) Top, schematic of cadaverine biosynthesis from L-lysine. Bottom, bacterial enzymes that catalyze this reaction include LydC, which is constitutively expressed and CadA, whose gene expression is induced at low pH.

(B) Dose-response curves for cadaverine against HRH family receptors.

(C) Dose-response curves (bottom) of bacterial polyamines (above) against HRH family receptors.

Receptor symbols are labeled as in (B). All dose-response curves were run in duplicate. Error bars are standard deviation. Error bars that are shorter than the height of the symbol are not shown.