But why is TRA-1 only inhibiting male-specific genes in hermaphrodites and not in males? TRA-1 activity is regulated by a signalling cascade: in males, the hermaphrodite-1 (HER-1) protein binds the transmembrane protein TRA-2 extracellularly and thereby inhibits the binding and processing of the intracellular domain of TRA-2 by TRA-3