Each ERBB receptor has distinct locations and numbers of tyrosine phosphorylation sites on its C-terminal tails; there are twelve on ERBB1, six on ERBB2, and eleven on ERBB3 (Jones et al.

Interestingly, when ErbB2 is overexpressed, heterodimers form preferentially. Unlike homodimers, which are either inactive (ErbB3 homodimers) or signal only weakly, ErbB2-containing heterodimers ...