section 23.6
Degradation of DNA
531
TABLE 23-1
Some Restriction Endonucleases and Their Cleavage Sites*
Microorganism
Name of Enzyme
Generates cohesive ends
E sch erichia coli
RY 13
EcoRI
B acillu s am yloliqu efacien s
H
BamHI
B acillu s glo b ig ii
BgHI
H aem ophilus aegyptiu s
Haell
H aem ophilus influenzae
Rd
Hindlll
P roviden cia stu artii
PstI
S treptom yces albu s
G
Sail
X anthom onas b a d rii
Xbal
Therm us aqu aticu s
TaqI
N ocardia otitdis
Not I
S treptom yces
sp.
Sgfl
Generates flush ends
B revibacteriu m albidum
Ball
H aem ophilus a egyptiu s
Hael
S erra tia m arcescen s
Smal
Target Sequence and Cleavage Sites
Axis of symmetry
G
f A
A
C
T
T
G
fG
A
C
C
T
A
i G
A
T
c
T
Pu
G
C
Py
Tc
G
A
i A
G
T
T
C
c
T
G
G TA
C
G i t
C
c
TA
G
T
c
T
A
G
TA
T
C
A
G
G
C
l G
G
C
G
C
C
G
C
G
A
C
G
C
î t
T
G
G
A
C
C
A \ G
G
T
C
C
C
C
C
G
G
G
! t
T
C
A
AT G
! t
C
C
A
GT G
!
T
C
T
!
A
GT A
i
G
CT Py
!
c
G
Pu
i
c
T
T
G
AT A
i
C
AT G
G
T
C
G
A
C
G
T T G
A
G
A
T
CT
T
!
G
A
i
C Î T
!
G
C
G
G
G
y
C
!
T 1 C
G
j
A
G
C
j e
C
A
iG
G
T
I
C
c l
iG
c l
\Ay
ÎG
G
G
iC
C
C
C
G
C
G
*The vertical dashed line indicates the axis of dyad symmetry in each sequence. Arrows indicate the sites of cutting. The enzyme TaqI yields
cohesive ends consisting of two nucleotides, whereas the cohesive ends produced by the other enzymes contain four nucleotides. The enzyme Hael
recognizes the sequence GGCC whether the adjacent pair is A -T or T -A, as long as dyad symmetry is retained. Pu and Py refer to any purine and
n v ri m i
à
i n p rp ç n p r f i v pI v
are useful for constructing novel DNA molecules, which
is the goal of
recombinant DNA (rDNA)
technology.
Since a restriction enzyme recognizes a unique se-
quence, the number of cuts and the number of DNA frag-
ments depends on the size of the molecule. In general,
restriction sites consisting of four bases will occur more
frequently by chance than sites consisting of six or eight
bases. Thus, four-cutters will generate more fragments
than six-cutters which, in turn, will generate more frag-
ments than eight-cutters.
A particular restriction enzyme generates a unique
family of fragments for a particular DNA molecule.
