Figure 6

Presynaptic proteins participate in interconnected protein-protein graphs. The protein-interacting graphs are extracted from STRING tool and supported by the literature, experimental data, and strong homology inference. Only high confidence interactions are shown (see Materials and methods). The central protein in each graph (marked with a red frame) is a representative for (a) synaptojanin 1 (SYNJ1; a key signaling protein in endocytosis), (b) NRXN1 (in presynaptic membrane interaction and synaptogenesis), (c) ERC2 (an active zone organizer), (d) RIMS (a genuine component of the active zone), and (e) vehicle-associated membrane protein (VAMP)8 (a component of the exocytosis). Protein names are according to the official gene symbols (as in Table 1 and Additional data file 2). Protein valences (the number of direct edges from the vertex) are marked in parenthesis. Note that the graphs for RIMS, ERC2, and NRXN1 are of a relatively low connectivity. Protein vertices are colored according to the conservation index; proteins with a sequence similarity above 65% relative to a human homolog are framed in black, otherwise they are marked in light blue. Proteins that were missing in one or more of the insect representatives are framed in orange. Proteins that do not have insect homologs (as in Table 1 and Additional data file 2) are marked by a yellow circle. A quantitative measure for the density of protein-protein interactions in the graph is added as well as the network conservation score (Con).