Abstract
The specificity in topology of the protein network of yeast was investigated by analysis of the number of the protein-protein interactions. In order to examine the specificity of the protein network, the proteins was classified into three layers; the low, middle, and high with respect to the number of the protein-protein interactions. In the middle layer, proteins were mainly interconnected to each other, so proteins in the high layer were forced to be wired to those in the low layer. Hence, the results indicates that the proteins in the high layer connected between the low layer and the middle layer and integrated the network as a whole. Chracterization of each layer was carried out biologically. It seems that in the past, studies have been focussed on the proteins in the high layer (highly connected proteins), but in the future, studies on the proteins in the middle layer will be more siginificant topologically and biologically.
