The relationship between sequence identity and pair coverage ( PC ) of 459 pairs of related hetero dimers. Among 459 pairs of related heterodimers, the sequence identities of 280 related heterodimer pairs are > 30%. In 280 related heterodimer pairs with > 30% sequence identity, there are 91% (256/280) pairs with PC ≥ 0.4. The rate of exception (PC < 0.4) is only 9%. The dots in gray box are the exceptions of the pairs with > 30% sequence identity but pair coverage < 0.4.