|
Figure 1.
Figure 1. (A,B) Ribbon diagrams of the regulatory domains
of KdpE[N]-BeF[3]^- (gold) and TorR[N] (protomers A and B,
teal). The two proteins form symmetric dimers mediated by the
 4-  5- 5 faces. In
KdpE[N]-BeF[3]^- the side chains of Asp53, Ser79, and Tyr98
(gray and red), and BeF[3]^- (magenta and salmon) are shown as
stick models, and the Mg2+ ion (orange) is shown in sphere
representation. BeF[3]^- is noncovalently bound to the site of
phosphorylation, Asp52, and serves as one of the ligands for the
catalytic Mg2+. Ser79 and Tyr98 are conserved residues involved
in the "switch" mechanism of activation associated with
phosphorylation of the conserved Asp52. The equivalent residues
Asp53, Thr80, and Tyr99 are shown for TorR[N]. (C) Alignment of
KdpE[N]-Ca2+ (protomer B, green) vs. KdpE[N]-BeF[3]^- (protomer
B, gold) showing the conserved residues involved in propagation
of the activation signal from the active site aspartate to the
4- 5- 5 face. The
side chains of Asp52, Ser79, and Tyr98 (oxygens in red), and
BeF[3]^- (magenta and salmon) are shown in stick representation,
with the Mg2+ (orange) and Ca^2+ (green) ions shown as spheres.
The 4- 4 loops are
further stabilized into a fixed conformation by interacting with
Tyr98. Minimal differences are seen between the two structures.
(D) Alignment of the four protomers found in the asymmetric unit
of the TorR[N] crystals. Side chains of Asp53, Thr80, and Tyr99
(oxygens in red) are shown as sticks. Two dimers are formed
between protomers A-B and C-D. Protomers A and D (teal) have the
switch residues Thr80 and Tyr99 in an inward active
conformation, while in protomers B and C (brown) they adopt an
outward conformation associated with the inactive state. The
conformation of the 4- 4 loops in
protomers B and C differs from that of protomers A and D because
side chains of residues in these loops are used for crystal
contacts.
|
