ATP-binding motifs in the IncC1 and IncC2 proteins. The Walker-like A and B boxes and motifs 2 and 3 are represented on a schematic of the IncC1 and IncC2 proteins. The Walker-like A and B boxes are described in the text. Motifs 2 and 3, also known as the A’ and B’ boxes, respectively, are conserved motifs that are also predicted to be part of the nucleotide-binding pocket (Koonin, 1993; Leonard et al., 2005a; Motallebi-Veshareh et al., 1990). The amino acid sequences of the core segments of the Walker-like A and B boxes are shown below the schematic. Upper numbers that flank the sequences refer to IncC1 amino acid residues; lower numbers refer to IncC2 residues. The residues targeted for mutation within IncC2 are lysine 10, lysine 15 and threonine 16. All were mutated to alanines. The schematic is drawn approximately to scale.