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Figure 2.
Figure 2. The structure of M. tuberculosis NusA is
consistent with a nucleic acid binding protein. (a) Sequence
comparison of NusA homologs. The secondary structure derived
from M. tuberculosis NusA is shown under the sequence. The
shaded regions refer to different structural motifs and are
maintained in the structures shown in (b). It is interesting to
compare the sequences of M. leprae and M. smegmatis NusA with
that of M. tuberculosis in the C-terminal proline-rich region,
in particular a poly(proline)stretch (PPPPPGQP) in M.
tuberculosis NusA which is (PPCSAGQS) in M. leprae and (AP-VG-)
in M. smegmatis. This poly(proline) sequence is totally absent
in the other homologues. (b) Structural comparisons of the main
motifs. The N-terminal domain of NusA compared to the B chain of
the rad50cd ABC ATPase, the S1 domain compared to the solution
structure of the S1 domain from polynucleotide phosphorylase,
and the KH domain compared to the canonical KH domain from the
nova KH3 structure.
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