Figure 1.

Response of major and minor receptors to attractants. Dose responses of wild-type cells to ligands of major (A) and minor receptors (B). Cells were stimulated by step-like addition of increasing amounts of attractant. The following abbreviations are used here and throughout: Asp, L-aspartate; MeAsp, α-methyl-DL-aspartate; Ser, L-serine; AiBu, α-aminoisobutyrate; Mal, maltose; Gal, galactose; Rib, ribose; Pro-Leu, proline-leucine dipeptide. Resulting initial changes in kinase activity were measured using a FRET activity reporter (see main text and Materials and methods). After each stimulation, the cells were re-adapted to buffer. The response for each step was normalized to the response of buffer-adapted cells towards a saturating stimulus of 100 μM MeAsp. (C) Threshold sensitivity S_T, determined as EC₅₀⁻¹ from Hill fits to the dose-response curves of individual experiments. Error bars indicate standard errors.