3 The ATP-dependent Restriction Enzymes

Abstract

I. INTRODUCTION
Restriction and modification of phages by bacteria were first described more than 40 years ago by Luria and Human (1952) for T-even phages and by Bertani and Weigle (1953) for the phages P2 and λ. The basic observation was that phages grown on one bacterial strain would grow poorly when tested on certain other related bacterial strains. Upon closer investigation, the poor growth was found to be an all or nothing affair. Most infected cells produced no phage at all; in the terminology that was adopted, the phages were restricted, although a few cells produced a normal yield of phage particles. The few phages that did result from the infection were modified so that they grew normally on the new host when tested in a second cycle of infection. Often, they were now restricted by the original host. The phenomenon of modification is Lamarckian rather than Mendelian in character since it is an adaptive response of the virus to the host that is lost when the virus is passaged through other cells.

Some 10 years after the discovery of restriction and modification, the first of a series of papers from Arber’s laboratory appeared that offered a molecular explanation for the effect (Arber and Dussoix 1962; Dussoix and Arber 1962). Both restriction and modification were properties of the DNA of the infecting phage. Restriction was due to the action of a nuclease that recognized specific sequences in incoming DNA as a signal to cleave it; modification was due to...