▁t cd E , ▁encoded ▁between ▁t cd A ▁and ▁t cd B , ▁enc odes ▁a ▁ 1 6 6 ▁am ino ▁a cy l ▁( aa ) ▁protein ▁which ▁causes ▁death ▁to ▁E . ▁col i ▁when ▁expressed , ▁and ▁the ▁structure ▁of ▁T cd E ▁res emb les ▁hol ins . ▁T cd E ▁acts ▁on ▁the ▁b acter ial ▁memb rane . ▁Since ▁T cd A ▁and ▁T cd B ▁lack ▁signal ▁pe pt ides , ▁they ▁may ▁be ▁released ▁via ▁T cd E ▁either ▁prior ▁to ▁or ▁subsequent ▁to ▁cell ▁l ysis . ▁Other ▁Clo str id ial ▁species ▁bear ▁hom olog ues ▁of ▁T cd E . ▁ ▁The ▁transport ▁reaction ▁believed ▁to ▁be ▁catal yz ed ▁by ▁T cd E ▁is : To x in ▁( in ) ▁→ ▁To x in ▁( out ) ▁ ▁See ▁also ▁▁ ▁Hol in ▁ ▁L ys in ▁ ▁Clo str id ium ▁diff icile ▁to x in ▁A ▁ ▁Clo str id ium ▁diff icile ▁to x in ▁B ▁ ▁Trans porter ▁Classification ▁Database ▁ ▁Further ▁reading ▁▁ ▁D ing le , ▁Kate ▁E .; ▁Elli ott , ▁Br iony ; ▁Robinson , ▁Est her ; ▁Griff ith s , ▁David ; ▁E y re , ▁David ▁W .; ▁Sto esser , ▁N icole ; ▁V aug han , ▁Al ison ; ▁Gol ub ch ik , ▁T anya ; ▁F aw ley , ▁Warren ▁N . ▁( 2 0 1 4 - 0 1 - 0 1