▁domains . ▁ ▁The ▁segments ▁N - term inal ▁and ▁far ▁C - term inal ▁to ▁the ▁AR M ▁domain ▁do ▁not ▁adopt ▁any ▁structure ▁in ▁solution ▁by ▁themselves . ▁Yet ▁these ▁intr ins ically ▁dis ordered ▁regions ▁play ▁a ▁cru cial ▁role ▁in ▁beta - c aten in ▁function . ▁The ▁N - term inal ▁dis ordered ▁region ▁contains ▁a ▁conser ved ▁short ▁linear ▁mot if ▁responsible ▁for ▁binding ▁of ▁Tr CP 1 ▁( also ▁known ▁as ▁ β - Tr CP ) ▁E 3 ▁u bi quit in ▁lig ase ▁– ▁but ▁only ▁when ▁it ▁is ▁ph osph ory l ated . ▁D eg rad ation ▁of ▁ β - c aten in ▁is ▁thus ▁medi ated ▁by ▁this ▁N - term inal ▁segment . ▁The ▁C - term inal ▁region , ▁on ▁the ▁other ▁hand , ▁is ▁a ▁strong ▁trans activ ator ▁when ▁rec ru ited ▁onto ▁DNA . ▁This ▁segment ▁is ▁not ▁fully ▁dis ordered : ▁part ▁of ▁the ▁C - term inal ▁extension ▁forms ▁a ▁stable ▁hel ix ▁that ▁pack s ▁against ▁the ▁AR M ▁domain , ▁but ▁may ▁also ▁eng age ▁separate ▁binding ▁partners . ▁This ▁small ▁struct ural ▁element ▁( Hel ix C ) ▁caps ▁the ▁C - term inal ▁end ▁of ▁the ▁AR M ▁domain , ▁shield ing ▁its ▁hydro ph ob ic ▁resid ues . ▁Hel ix C ▁is ▁not ▁necessary ▁for ▁beta - c aten in ▁to ▁function ▁in ▁cell - cell ▁ad hes ion . ▁On ▁the ▁other ▁hand , ▁it ▁is