Figure 2.
FIGURE 2. Substrate binding in plant GCL. A, close-up view
of the glutamate binding site with the inhibitor BSO (in yellow;
sulfur depicted in magenta) in bond representation and including
the final 2F[obs] - F[calc] electron density map contoured at
1.5 . Residues reaching
from the central -sheet (in blue) to
coordinate the Mg^2+ ion (in cyan) are depicted in blue.
Residues contributed by the helical arms are shown in light
green. B, schematic representation of the inhibitor BSO binding
to BjGCL. The LigPlot diagram (50) summarizes key interactions
between the BSO ligand and active site residues. Yellow lines,
BSO ligand; green lines, BjGCL residues; semicircles with
radiating lines; atoms or residues involved in hydrophobic
contacts between protein and ligand. C, stereo close-up view of
the plant GCL cysteine binding pocket formed by mostly
hydrophobic residues (in blue) around the aliphatic side chain
of BSO (in light gray). The corresponding secondary structure
elements and residues in E. coli GCL (PDB-ID: 1VA6) are shown in
orange. D, known mutations in the Arabidopsis GCL gene are in
proximity of the substrate binding sites in plant GCL. BjGCL in
ribbon representation is shown with BSO and ADP (modeled) in
bonds representation (in yellow). Small spheres indicate the
positions of residues affected in AtGCL mutant plants (in
magenta). Enlarged versions provide models on how the affected
residues in rax1-1 and rml1 mutants may interact with GCL
substrates. The rax1-1 arginine residue (Arg^220) is shown in a
modeled rotamer configuration bringing its guanidinium group in
close proximity to the terminal methyl of BSO that corresponds
to the sulfhydryl group of cysteine (in green). Interactions are
highlighted by dotted lines (in magenta).
The above figure is reprinted
by permission from the ASBMB:
J Biol Chem
(2006,
281,
27557-27565)
copyright 2006.
. Residues reaching
from the central 
-sheet (in blue) to
coordinate the Mg^2+ ion (in cyan) are depicted in blue.
Residues contributed by the helical arms are shown in light
green. B, schematic representation of the inhibitor BSO binding
to BjGCL. The LigPlot diagram (50) summarizes key interactions
between the BSO ligand and active site residues. Yellow lines,
BSO ligand; green lines, BjGCL residues; semicircles with
radiating lines; atoms or residues involved in hydrophobic
contacts between protein and ligand. C, stereo close-up view of
the plant GCL cysteine binding pocket formed by mostly
hydrophobic residues (in blue) around the aliphatic side chain
of BSO (in light gray). The corresponding secondary structure
elements and residues in E. coli GCL (PDB-ID: 1VA6) are shown in
orange. D, known mutations in the Arabidopsis GCL gene are in
proximity of the substrate binding sites in plant GCL. BjGCL in
ribbon representation is shown with BSO and ADP (modeled) in
bonds representation (in yellow). Small spheres indicate the
positions of residues affected in AtGCL mutant plants (in
magenta). Enlarged versions provide models on how the affected
residues in rax1-1 and rml1 mutants may interact with GCL
substrates. The rax1-1 arginine residue (Arg^220) is shown in a
modeled rotamer configuration bringing its guanidinium group in
close proximity to the terminal methyl of BSO that corresponds
to the sulfhydryl group of cysteine (in green). Interactions are
highlighted by dotted lines (in magenta).