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Figure 7.
Figure 7. Comparison of the surfaces of SUMO-1 (a and b)
and ubiquitin (c and d). Shown are two opposite surface views of
SUMO-1 and ubiquitin rotated around the longitudinal axis by
160° and by ±80° as compared to the front view
shown in Figure 5 and Figure 6. The corresponding orientations
are indicated by the C^α backbone visible underneath the
surface. The charge topology was calculated and coloured
according to the electrostatic potential over a range of
approximately −20 kT/e (in red) to +20 kT/e (in blue) using
the program GRASP [Nicholls et al 1991]. The first view of
SUMO-1 (a) displays positive charged epitopes (Arg54, Lys46,
Lys25, Lys23, Lys17 and Lys16) absent on the corresponding
surface of ubiquitin (c) with the exception of SUMO-1 Lys25 (a),
and ubiquitin Lys6 (c). The second view of SUMO-1 (b) reveals a
large negatively charged surface (Glu89, Asp86, Glu85 and Glu84)
together with a negatively charged pocket (Glu83, Glu18, Glu15,
Asp12, Glu11 and Glu20), which are not conserved on the
corresponding surface of ubiquitin (d).
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