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  • Title: [Mutational analysis of the conserved motif of the Arda anti-restriction protein encoded by self-transmissible IncI plasmid ColIb-p9].
    Author: Del'ver EP, Sobennikova MV, Belogurova NG, Nekrasov SV, Kolesnikova MD, Agafonova OV, Belogurov AA.
    Journal: Mol Biol (Mosk); 2002; 36(6):1062-7. PubMed ID: 12500545.
    Abstract:
    A study was made of the functional role of the ArdA antirestriction motif (130-LLADVPETVALYFD-143) conserved among all known Ard (alleviation of restriction of DNA) proteins, which are encoded by self-transmissible plasmids and specifically inhibit type I restriction-modification systems. Conserved residues of the motif were individually changed, and the resulting mutants tested for in vivo activity. Hydrophobic L130, L131, and V138 were substituted with negatively charged E; negatively charged D133, E136, and D143 substituted with hydrophobic V; and D127, D150, and D154 neighboring the antirestriction motif substituted with V. Four substitutions (L130E, L131E, V138E, and D143V) substantially (25-1000 times) reduced the ArdA activity. The other substitutions within or beyond the motif had no appreciable effect. Substitutions L130A and L131A each reduced the ArdA activity 10- to 20-fold, indicating that high hydrophobicity of L130 and L131 is important for the ArdA function. Thus, the antirestriction role of ArdA is indeed due to its conserved motif.
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