SITE-SPECIFIC DELETION OF THE N-TERMINAL SEGMENTS FROM EcoRI ENDONUCLEASE USING THE POLYMERASE CHAIN REACTION

We developed a general and efficient method for directing the deletions of DNA sequences of any lengths using polymerase chain reaction (PCR). The method was based on in vitro amplification of target sequences with site-specific deletions, Klenow end-flushing and blunt-end cloning. As an example, it was used to delete the restriction gene encoding EcoRI endonuclease, resulting in plasmids expressing two truncated forms. Assays using SDS-PAGE and gel retardation revealed the important role of the amphipathic helix (29-43) of the EcoRI endonuclease in binding to its cognate substrate.