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Figure 3.
Figure 3. Electron density maps. Unbiased F[o] -F[c]
difference Fourier maps (gray netting) contoured at 3.0s reveal
the location, orientation, and conformation of these
antibiotics. (a), (b) Nucleotides of ribosomal RNA (gray sticks)
that are either protected or deprotected by the anisomycin (a)
or chloramphenicol (b) from chemical modification (green) or
that upon mutation confer resistance to the given antibiotic
(orange) are provided for context. (c) The placement and
conformation of virginiamycin M (blue) in the corresponding
doughnut shaped electron density is unambiguous. (d) Blasticidin
S (purple) binds at two sites, but density for the second site
is weaker and incomplete. (e) Sparsomycin (green) binds only in
the presence of a P-site bound substrate (orange). A2637 (2602)
(gray stick) is apparent in the difference map because it
changes conformation upon substrate binding.
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