Figure 4.
Figure 4: Detailed view of SAM recognition by the riboswitch.
a, Stereo view of the SAM-binding pocket comprising the P1 and
P3 helices and J1/2. b, Hydrogen-bonding interactions between
the adenine base of SAM, A45 and U57. The experimental electron
density map is shown as an orange cage, contoured at 1.25
. c, Interactions between the main chain atoms of
methionine and the G58–C44 pair in P3 and G11 of J1/2.
Distances in b and c are given in ångströms. d, SAM
binding to the P1 helix; selectivity for SAM is probably
mediated through electrostatic interactions with the carbonyl O2
of U7 and U88 (double-headed arrows). e, Ligand-induced
interactions between the P3 helix and the 3' side of the P1
helix (black dashed lines).
The above figure is reprinted
by permission from Macmillan Publishers Ltd:
Nature
(2006,
441,
1172-1175)
copyright 2006.
. c, Interactions between the main chain atoms of
methionine and the G58–C44 pair in P3 and G11 of J1/2.
Distances in b and c are given in ångströms. d, SAM
binding to the P1 helix; selectivity for SAM is probably
mediated through electrostatic interactions with the carbonyl O2
of U7 and U88 (double-headed arrows). e, Ligand-induced
interactions between the P3 helix and the 3' side of the P1
helix (black dashed lines).