BIOINORGANIC CHEMISTRY A Short Course Second Edition

C–G U A

G–C

G U

U G

C–G

C–G

C–G

G–C

U–A

C–G

A–UG–C

UAGA

AAU

A–U

C–G

C–GU•180AU

GGG

A G

U G

A A

A A

G U

G U

C–G

AAGG

P4–P6 P1–P2.1 P3–P9

UJ3/4

C A

U J6/7

3 ′

5 ′

• (^110260)
C–G
C–G
C–C
G–C
C–G
C–G
C–G
G U
U–A
C–G
A–U
A–U
C–G
A–U
AUG–C
UUC
U A
AA
A–U
U–A
U
•250
•240
A
A G
G U
U–A
C–G
U–A
P5bC–G
Tetraloop
(L5b) Tetraloopreceptor
(J6a/6b)
220 •
P6a
P6b
230 •
L6b
A–U
G–C
G A
AA
G U
G U
AAA
L5c P4
P6
C A
AA
C
G
C
CCUUG
A-rich
bulge
P5
200 •
•120
P5a

• 190

130 •

J5/5a

GACA

ACA

J4/5

210•A

P5a

P5c

170

• 160

140 •

150 •

U G–U

3 ′

5 ′

Figure 6.4 Secondary structure of a group I intron ribozyme. (From Figure 1 of refer-
ence 13. Reprinted with permission of AAAS.)

C262

A261

A263

C311

A265

U310

C266

A306

Mg

Mg

U305

G312

G264

G309

ωG O 2 ’

ωG O 3 ’

non-bridging

phosphate O

non-bridging

phosphate O

ωG, G414

PDB: 1X8W numbering

Figure 6.6 Base triples surrounding Ω G in PDB: 1X8W. Magnesium ions in position
to facilitate nucleophilic attack. Visualized using Chem3D Ultra and ChemDraw Ultra,
version 10.0. (Printed with permission of CambridgeSoft Corporation.)