passages.id: split_4_test_2789_passage
passages.type: progene_text
passages.text: Single mutational substitutions of negatively charged amino acid residues located in the " antirestriction motif " with hydrophobic alanine , E134A , E137A , D144A , or a double substitution E134A , E137A do not affect the antirestriction activity ( Ard ) of ArdA but almost completely abolish the antimodification activity ( Amd ) .