Figure 4. Exonuclease and NDP kinase activity of purified human NDK1 mutants.
A. Ni-NTA column-purified human wild type and mutant NDK1 proteins on an SDS-PAGE gel. B. Exonuclease activity of purified human wild type and mutant NDK1 proteins was tested with a single-stranded 30-mer oligonucleotide and equal amounts (100 ng) of purified proteins. C. Enzymatic assay for nucleoside diphosphate kinase activity. D54A, E5Q and E5A mutants retained relatively high kinase activity.