I am looking at a particular gene (n=1), the gene is involved in a variety of molecular functions like signal transduction, molecular binding etc. What will be the best way to summarize the function of such a gene ? I am thinking of analyzing individual interactome of it's protein product(less direct interaction, but good number of interactions via STRING (confidence score=0.4)) and use BiNGO to derive the over-all function. Do we have any better approach to illustrate functional diversity of a single gene ?
The approach you suggest is sound, however, I personally do not think that a list of GO terms is a particularly good way to summarize how a gene works. You already write yourself that the gene is involved in a variety of molecular functions, which I assume are GO molecular function terms. Including GO terms from its interaction parters will probably only give you an even longer list.
The best approach depends on whom you need to summarize it for. If it is for a biologist, and the gene is involved in signal transduction, the best way is probably a schematic drawing of how it is involved in which signaling processes (assuming that this is known). I know that this is not a nice computer-readable, ontology-based way of storing information, but when it comes to communicating complex information to a human being, it is difficult to beat a good figure.
You could also try GeneMANIA.
It's like STRING, but has more data and it does the GO enrichment analysis for you (go to the functions tab). By default, it doesn't incorporate information about protein domains but you can change that by activating that network in the advanced options panel.