Structural Studies of ECO RV Endonuclease and of its Complexes with Short DNA Fragments
Many bacteria restrict the expression of foreign DNA introduced through phage infection, conjugation or transformation. At the molecular level such host-controlled restriction is the result of an endonuclease activity which cuts foreign DNA and a modification activity which protects the host’s DNA against this cleavage. Of the three types of restriction-modification systems usually distinguished the type II systems are the simplest and consist of two separate enzymes, an endonuclease and a methylase which recognize the same sequence of typically 4 to 6 base pairs. The endonucleases cleave double stranded DNA at these recognition sites in the presence of Mg2+ ions. Their remarkable specificity and its modulation by various factors make them attractive systems for structurally oriented studies of protein nucleic acid interactions (for a recent review see Modrich and Roberts1).
KeywordsMolecular Replacement Twofold Axis Helix Axis Wire Model Protein Nucleic Acid Interaction
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