ph rin - A 2 , ▁by ▁obser ving ▁ax on ▁growth ▁in ▁ret inal ▁t issue ▁culture ▁on ▁a ▁strip ed ▁car pet ▁of ▁anterior ▁and ▁posterior ▁t ect um ▁memb rane . ▁ ▁E phr ins ▁are ▁divided ▁into ▁ 2 ▁classes : ▁E ph rin - As ▁are ▁bound ▁to ▁the ▁memb rane ▁through ▁G PI ▁( gly cos yl ph osph at id y lin os it ol ) ▁link age ▁and ▁E ph rin - B s ▁have ▁a ▁transm emb rane ▁domain ▁and ▁a ▁short ▁cy top las mic ▁domain ; ▁they ▁interact ▁with ▁their ▁respective ▁re cept ors ▁E ph - A ▁and ▁E ph - B ▁which ▁are ▁members ▁of ▁the ▁ty ros ine ▁kin ase ▁family . ▁One ▁unusual ▁feature ▁about ▁E phr ins ▁is ▁their ▁ability ▁to ▁bid irection ally ▁signal ▁( Fig . 4 ); ▁they ▁can ▁particip ate ▁in ▁both ▁forward ▁( lig and ▁to ▁re ceptor ) ▁and ▁reverse ▁signal ing ▁( re ceptor ▁to ▁lig and ). ▁E ph / E ph rin ▁binding ▁indu ces ▁conform ational ▁changes ▁in ▁the ▁E ph rin ▁transm emb rane ▁and ▁cy top las mic ▁domains , ▁activ ating ▁the ▁signal ing ▁path way . ▁E ph / E ph rin ▁forward ▁signal ing ▁regul ates ▁act in ▁dynamics ▁via ▁small ▁G TP ases ▁of ▁the ▁R ho ▁family ; ▁reverse ▁signal ing ▁occurs ▁when ▁the ▁E ph rin - B ▁cy top las mic ▁tail ▁gets ▁ph osph ory l ated