Molecular and Structural alterations in a number of mutants affected in AdK. (A) Partial sequence alignment of AdK from a number of species showing the conserved residues that are altered in the FomR-4, VF18, VF19 and DrToyR-18 mutants. The NxxE motif in the sequence alignment is boxed. Of the two numbers shown for various amino acids that are altered in these mutants, the first corresponds to the position of the amino acids in the AdK-L isoform for Chinese hamster cells, whereas the latter numbers (in parenthesis) refer to their positions in the human AdK-S sequence, whose structure is shown below. (B) A close up view of human AdK structure  showing the position of the Glu242(226) residue that is altered in the DrToyR-18 mutant. Magnesium is shown as purple spheres and the conserved Asn239(223) and Glu242(226) residues of the NxxE motif are shown in magenta and blue colors, respectively. The proximity of the NxxE motif to Mg2+ and the substrate adenosine is shown. (C) A close up view of the human AdK-S structure showing the locations of various amino acids that are altered in the FomR-4, VF18 and VF19 mutants. The substrate Ado is shown in red.