While other replacements of the lysine residues still allowed interaction with nucleotides as demonstrated by photocrosslinking with the analog 8-azido ATP enhancement of fluorescence of trinitrophenyl-ATP. a change to asparagine also eliminated the nucleotide-binding activity. Wilken, Schmees and Schneider, unpublished). Similarly, substitutions of the conserved aspartate residue in site B were generally shown to abolish ATPase activity and nucleotide binding