Fig. 1.

Sequence conservation for DHp and Che phosphatase helices. These sequence logos display the relative frequency and information content at each position in a collection of aligned sequences (20). Numbering is according to the (A) E. coli NarX (HisKA_3), (B) CheZ, (C) EnvZ (HisKA), and (D) B. burgdorferi CheX sequences. Hydrophobic residues that define coiled-coil heptad repeats in the HisKA_3 and CheZ sequences are denoted by lowercase letters; residues marked “x” represent “skip” positions (21). The H-box motif is indicated for the DHp sequences. The conserved DxxxQ, E/DxxT/N, and ExxN motifs are described in the text.