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Figure 1.
Figure 1. (a) The N-terminal (green) , S1 (yellow), KH1
(blue) and KH2 (magenta) domains of NusA from M. tuberculosis
represented as ribbons in two perpendicular orientations. The
alpha-helices and strands are labelled according to the order in
which they occur in the sequence. NusA can be regarded as being
made up of two components, an N-terminal domain with a a[3]b[3]
structure (comprising helices H1 to H3 and strands S1 to S3)
linked to the C-terminal module which has a S1-like region
(five-stranded beta-barrel S4-S8, with a turn of a 3[10]-helix
H4) followed by two K homology domains, also with a[3]b[3]
structure, KH1(H6-H8, S9-S11) and KH2 (H9-H11, S12-S14). (b) The
NusA molecule with the residues H-bonded at the interfaces
shown. The conserved residues are labelled. In this view the KH1
domain can be seen to form a wedge between the S1 and KH2
domains. (c) An enlarged view of the interfaces with KH1 at the
centre. It shows the H-bonding networks around the partly buried
Arg183 in S1 and Arg231 in KH1, and the completely buried Lys219
in KH1.
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