Figure 4.
Fig. 4. ATP binding by AlaRS. (A) Simulated annealed omit
F[o] - F[c] electron density map (resolution, 2.15 Å;
contour, 2.8 ) for the active site
region of AlaRS[453]/Mg2+-ATP complex, superimposed on the
refined model. The model for ATP, magnesium ions, and
surrounding atoms within a sphere of 3.2 Å was omitted
from map calculation. (B) Similar view showing active site
residues involved in ATP or magnesium binding. Model colors are
as in Fig. 1. Bound magnesium ions and water molecules are shown
as gray and red spheres, respectively. For clarity, some water
molecules and interactions with the ribose are not shown. (C)
Schematic of the interactions between enzyme, ATP, and
magnesium. Residues from motifs 2 and 3 are shown in orange and
cyan, respectively. Residues in black belong to strands in the
central -sheet of the
active-site domain. Side chain conservation patterns among AlaRS
sequences from 80 organisms are shown in brackets (percentage
occurrence shown only for side chains present in >4% of the
sequences). Side chains without adjacent bracketed numbers are
invariant.
) for the active site
region of AlaRS[453]/Mg2+-ATP complex, superimposed on the
refined model. The model for ATP, magnesium ions, and
surrounding atoms within a sphere of 3.2 Å was omitted
from map calculation. (B) Similar view showing active site
residues involved in ATP or magnesium binding. Model colors are
as in Fig. 1. Bound magnesium ions and water molecules are shown
as gray and red spheres, respectively. For clarity, some water
molecules and interactions with the ribose are not shown. (C)
Schematic of the interactions between enzyme, ATP, and
magnesium. Residues from motifs 2 and 3 are shown in orange and
cyan, respectively. Residues in black belong to strands in the
central 
-sheet of the
active-site domain. Side chain conservation patterns among AlaRS
sequences from 80 organisms are shown in brackets (percentage
occurrence shown only for side chains present in >4% of the
sequences). Side chains without adjacent bracketed numbers are
invariant.