The normalized depth for all the proteins in the 335 Pfam families ( Figure 3D, top) is analyzed in view of the distribution of the normalized depth of the viral proteins within these families ( Figure 3D, bottom) . It seems that the two distributions are remarkably different ( Figure 3D ) which is in accord with the notion that the viral proteins are relatively isolated subsets among the proteins from the cellular organisms in the relevant Pfam families. Table 2 shows a sample of these families along with the cellular process and the protein function in the viral life cycle. A full list of the 667 Pfam families with the analyzed properties of their alignment trees is provided in Supportive data Table S3 .