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Figure 3.
Fig. 3. Structure of the Vitamin B12 binding site of
BtuF. A, stereo pair of the B12-binding site of BtuF colored as
in Fig. 1A, with conserved waters represented as green spheres.
The side chains of relevant residues are depicted in
ball-and-stick representation colored by domain with associated
nitrogen and oxygen atoms blue and red, respectively. Direct and
water-mediated H-bonds are represented by red and green dotted
lines, respectively. B, surface representation of the likely
BtuCD-interacting face of BtuF color-ramped according to
sequence conservation, with white indicating no conservation and
burgundy indicating 100% conservation in the five known BtuFs.
C, surface representation of the same face of BtuF color-ramped
according to electrostatic potential, with red indicating
negative potential, blue indicating positive potential, and
fully saturated colors indicating potential  ± 5 kT
(assuming an ionic strength of 100 mM).
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