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![[Figure 4]](ba5246fig4mag.jpg)
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Figure 4
Sequence assignment and validation of the 50-residue (70 Å long) CSN7 C-terminal helix. (a) The location of the helix (highlighted in blue) in CSN (white in cartoon mode). The initial sequence assignment was anchored on a prominent side-chain bump for Trp177 in an electron-density map calculated by cross-crystal averaging across the three refinement data sets for crystal c343 with DMMULTI at 4.0 Å resolution prior to side-chain modelling.. (b) A segment of this electron-density map (grey mesh) contoured at 1 r.m.s. with a radius of 4 Å around the CSN7 C-terminal helix. (c) The same view as in (b) with the final model embedded (shown in cartoon mode with side chains in blue). The sequence registered was confirmed with a peak found for a modified Cys residue neighbouring Trp177 in an anomalous LLG map (pink mesh; peak height of 6.3 r.m.s.d.) calculated for an Hg-derivative crystal. Additionally, Trp177 has been identified biochemically as crucial for the interaction of CSN7 with CSN6 (Kotiguda et al., 2012  ). The side chain of Trp177 of CSN7 is buried in a hydrophobic pocket created by CSN6 in CSN, explaining the biochemical findings. |
![[Figure 4]](ba5246fig4.jpg)
 | STRUCTURAL BIOLOGY |
ISSN: 2059-7983
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