Figure 1

Construction of a GC search motif based on the catalytic center of characterized GCs in Arabidopsis thaliana . The GC catalytic centers in the alignment of all previously characterized GCs in Arabidopsis (A), is represented in the red box while the blue box implicates binding with Mg²⁺ or Mn²⁺ ions. A 14 amino acid long GC search motif (B) was built by including all the residues present in each position of the catalytic center. The amino acid substitutions are in square brackets ([ ]), “X” stands for any amino acid and the gap size is marked in curly brackets ({ }). Underlined amino acids have been added to the motif because of their chemical similarity to the amino acid at this position. Amino acids highlighted in red are functionally assigned residues; amino acid in position 1 forms the hydrogen bond with the guanine, amino acid in position 3 confers substrate specificity for GTP while amino acid in position 14 stabilizes the transition state from GTP to cGMP. The identification and assignment of functions to key residues of the GC motif are detailed in [7].