Biomedical Engineering Reference
In-Depth Information
Figure 5.
Map of the protein-protein interaction network of
S. cerevisiae
(24). The color code
of nodes refers to the phenotypic effect the deletion of the respective protein has on the organ-
ism (red: lethal; green: viable; orange: slowed growth; yellow: unknown).
kinases, immunoglobulins, and zinc-fingers played an important role. Interest-
ingly, the increasing complexity of an organism's domain architecture was found
to decrease the slope of the degree distribution, and highly connected domains
constantly accumulated links due to the organismic complexity. Similarly, inter-
actions of domain families generated from sequence and structural data (41,63)
revealed that highly connected domains on sequence level appear to be the most
frequently interacting as well.
4.4. Hierarchies in Biological Networks
The clustering coefficient of metabolic networks varies with the inverse
degree,
C
(
k
) ~
k
-1
, indicating the presence of a hierarchical modularity. In order
to discern the discrete modules, we can define a topological overlap, which
