Figure 3 continued
Figure 3. A, Amino acid sequence comparison of sensor domains from different NtrY proteins. The sensor region is contained in the grey box. B, Amino acid sequence comparison of Azospirillum brasilense and Azorhizobium caulinodans NtrX proteins. The boxes show the receiver domain (a) and helix-turn-helix DNA-binding motif (d). The dotted boxes represent: ATP-binding site (underlined), RNA polymerase s54 factor interaction domain (c). The black box and the arrow indicate the phosphorylation site (b). Identical amino acids are indicated by an asterisk, conserved substitution by a colon, and semi-conserved substitution by a dot. Ac = Azorhizobium caulinodans; Ab = Azospirillum brasilense; Cc = Caulobacter crescentus; Sm = Sinorhizobium meliloti; Ml = Mesorhizobium loti.