When these 23 residues that are common among either two of the groups are highlighted on the structure of HER2, it clearly shows (Figure 5a), the converged region / binding pocket on the structure wherein these ligands bind with HER2. The cluster group residues are colored the same way as in Figure 3. When the pocket has been filled with only the 9 common residues (Figure 5b), it clearly indicates the functional groups that form the pocket to which the drug is expected to bind. The designing of a drug is based on these functional groups and is to be optimized so as to get a high affinity molecule with lowest binding constant.