Figure 5.
Fig. 5. (A) Electron density map of the region around the
mutated residue K83. The density for this residue is defined in
a 2F[o] F[c] map
contoured at 1 . The
positions of the next few residues of the native molecule are
colored in brown, and these residues are disordered. The next
residue is G84; this position is expected to show flexibility.
The helical arch does not show evidence of order in the electron
density map. The first well defined residue in helix 5 is F104.
The absence of density preceding this residue suggests that the
helix is unwound and exists in an undefined conformation. (B) A
stereo view of the metal-binding site MeI as determined in the
native molecule. The K83 side chain from the native molecule is
shown in black. The positions of the metal's ligands are largely
unchanged compared with the native (data not shown). The only
amino group in close proximity to MeI is that of K83 (distance
between NH[2] and MeI = 4.2 Å). (C) A C trace of
the native (red) and K83A mutant structures (yellow)
superimposed. Disordered residues in the mutant include 35-41
and 84-103. The regions around the acidic residues composing the
metal-binding site are very similar. (D) A space-filling model
of the protein, showing the three residues mutated in this study
in red (top to bottom: K83, K196, and K215) in relation to the
proposed threading mechanism. DNA is shown as colored strands
and the metal sites observed are shown as purple spheres.
F[c] map
contoured at 1 
. The
positions of the next few residues of the native molecule are
colored in brown, and these residues are disordered. The next
residue is G84; this position is expected to show flexibility.
The helical arch does not show evidence of order in the electron
density map. The first well defined residue in helix 5 is F104.
The absence of density preceding this residue suggests that the
helix is unwound and exists in an undefined conformation. (B) A
stereo view of the metal-binding site MeI as determined in the
native molecule. The K83 side chain from the native molecule is
shown in black. The positions of the metal's ligands are largely
unchanged compared with the native (data not shown). The only
amino group in close proximity to MeI is that of K83 (distance
between NH[2] and MeI = 4.2 Å). (C) A C 
trace of
the native (red) and K83A mutant structures (yellow)
superimposed. Disordered residues in the mutant include 35-41
and 84-103. The regions around the acidic residues composing the
metal-binding site are very similar. (D) A space-filling model
of the protein, showing the three residues mutated in this study
in red (top to bottom: K83, K196, and K215) in relation to the
proposed threading mechanism. DNA is shown as colored strands
and the metal sites observed are shown as purple spheres.