Methods in Molecular Biology • 16 Enzymes of Molecular Biology

CHAPTER 8

Restriction Enzymes

Alfred Pingoud, Ji rgen Alves,

and Robert Geiger

1. Introduction
   Restriction enzymes are endonucleases that recognize specific double-
   stranded DNA sequences and cleave the DNA in both strands, e.g.:

-GpApApTpTpC- -G pApApTpTpC-

--~ +

-CpTpTpApApG- -CpTpTpApAp G- (1)

They have been identified in many prokaryotic organisms and are
considered to be part of a defense system directed against foreign
DNA. Site-specific endodeoxyribonucleases are given EC numbers,
e.g., EC 3.1.21.4 for a Type II enzyme (see below).
The phenomenon of restriction and modification was discovered by
Bertani and Weigle (1), who noticed that bacteriophage ~, grown on E.
coli C could not be efficiently propagated on E. coli K. Once estab-
lished there, however, it would grow poorly on E. coli C. Similar
responses of bacteriophages to their hosts were observed in other sys-
tems. The molecular basis for this phenomenon was identified by Arber
and Dussoix (2), who demonstrated that the bacterial host contains a
restriction enzyme that destroys the bacteriophage DNA and a modi-
fication enzyme that protects the host DNA against the nucleolytic
activity of its own restriction enzyme. It was suggested that these
restriction enzymes recognized a specific DNA sequence and subse-
quently cleaved the DNA, unless it was modified by the companion

From: Methods in Molecular Biology, Vol. 16: Enzymes of Molecular Biology

Edited by: M. M. Burrell Copyright ©1993 Humana Press Inc., Totowa, NJ

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