6 0 - am ino ▁acid ▁long ▁domain ▁composed ▁of ▁three ▁alpha ▁hel ix es . ▁The ▁following ▁shows ▁the ▁cons ensus ▁home od om ain ▁( ~ 6 0 ▁am ino ▁acid ▁chain ): ▁▁▁▁▁▁▁▁▁▁▁▁▁ ▁Hel ix ▁ 1 ▁▁▁▁▁▁▁▁▁ ▁Hel ix ▁ 2 ▁▁▁▁▁▁▁▁ ▁Hel ix ▁ 3 / 4 ▁▁▁▁▁▁▁▁▁ ▁_ ________ ____ _ ▁▁▁ ▁_ ________ _ ▁▁▁ ▁_ ________________ ▁R R R K R TA Y TR Y QL LE LE KE F H F N RY L TR R R RI E LA H SL NL TER HI K I WF Q NR R M K W K K EN ▁.... | .... | .... | .... | .... | .... | .... | .... | .... | .... | .... | .... | ▁▁▁▁▁▁▁▁▁▁ 1 0 ▁▁▁▁▁▁▁▁ 2 0 ▁▁▁▁▁▁▁▁ 3 0 ▁▁▁▁▁▁▁▁ 4 0 ▁▁▁▁▁▁▁▁ 5 0 ▁▁▁▁▁▁▁▁ 6 0 ▁ ▁Hel ix ▁ 2 ▁and ▁hel ix ▁ 3 ▁form ▁a ▁so - called ▁hel ix - turn - hel ix ▁( HT H ) ▁structure , ▁where ▁the ▁two ▁alpha ▁hel ices ▁are ▁connected ▁by ▁a ▁short ▁loop ▁region . ▁The ▁N - term inal ▁two ▁hel ices ▁of ▁the ▁home od om ain ▁are ▁ant ip ar allel ▁and ▁the ▁longer ▁C - term inal ▁hel ix ▁is ▁roughly ▁per pend icular ▁to ▁the ▁axes ▁established ▁by ▁the ▁first ▁two . ▁It ▁is ▁this ▁third ▁hel ix ▁that ▁interact s ▁directly ▁with ▁DNA ▁via ▁a ▁number ▁of ▁hydro gen ▁b onds ▁and