3.3.3 Iota toxin-component has increased connectivity when bound
to actin protein.
The Iota toxin component Ia is an ADP ribosylating toxin (ADPRT). The
C-terminal domain that houses the active site of this protein complexed
to NAD is essential for its function. It is known that the active site
loop along with residues Tyr60-Tyr62 of the toxin binds to actin protein
and inhibits its activity. Actin specific ADPRTs perform ADP
ribosylation of G-actin at Arg117, leading to disorganisation of the
cytoskeleton and cell death.
In our analysis, significant dissimilarity is observed between the actin
bound form of the protein (PDB ID 3BUZ shown in Supplementary Figure 3C)
and the unbound toxin. The actin bound protein has few more new
interactions at the binding site and a net overall gain in connectivity.
New edges are found to be gained at the functional sites Arg352, Glu378,
Glu380 of the protein. A net gain in number of edges and hubs is
observed, which shows a more compact structure especially around the
binding site (Figure 2C).