(a) Mutant derivatives characterized in this study. Shadings for various membrane regions correspond to those used in Fig. 1. “Possible effects on AS1” indicates the structural forces expected at the AS1 helix if the TM2-AS1 segment were a continuous α-helix. Viewed from the membrane toward AS1, one-residue deletions should cause outward displacement and counter-clockwise rotation; one-residue insertions should cause inward displacement and clockwise rotation.
(b) Chemotactic behaviors mediated by Tsr deletion mutants. Derivatives of plasmid pPA114 were tested for ability to support chemotaxis of receptor-less host strain UU2612 on tryptone semi-solid agar containing 25 μg/ml chloramphenicol and 0.6 μM salicylate. Plates were photographed after incubation at 30°C for 7-8 hours.
(c) Chemotactic behaviors mediated by Tsr insertion mutants. Derivatives of plasmid pRR53 were tested for ability to support chemotaxis of receptor-less host strain UU2612 on tryptone semi-solid agar containing 100 μg/ml ampicillin and 100 μM IPTG. Plates were photographed after incubation at 30°C for 7-8 hours.