Fig. 2.

Amino acid replacements and chemotaxis phenotypes of Tsr control cable mutants. (A) Summary of the mutational survey. Plus symbols denote the wild-type residues. The Tsr phenotypes produced by various amino acid replacements at each of the five control cable residues are indicated by circles: Tsr⁺ (white), Tsr^+/− and Tsr^−/+ (gray), and Tsr⁻ (black). See the footnotes to Table 1 for an explanation of these phenotypes. (B) Examples of mutant receptor phenotypes. Tsr plasmids were introduced into strain UU2612, and transformant colonies were transferred to tryptone soft agar plates with toothpicks. The top plate contained 50 μg/ml ampicillin and 100 μM IPTG. The bottom plate contained 12.5 μg/ml chloramphenicol and 0.6 μM sodium salicylate. Plates were incubated for 7 h at 30°C. The wild-type parental plasmids used are pRR53 and pPA114. The corresponding empty vectors are pRR48 and pKG116. Tsr⁻: pRR48, I214D, I214P, I214R; pKG116, K215P. Tsr^−/+: I214E, I214K, A216P. Tsr^+/−: G213Y, I214H, I214L; S217I, S217V, S217L, S217M. Tsr⁺: pRR53, G213P; pPA114, S217A.