s ▁as ▁opposed ▁to ▁other ▁T A LE - lik es . ▁ ▁T - zero ▁ ▁Another ▁unique ▁feature ▁of ▁T A LE s ▁is ▁a ▁set ▁of ▁four ▁repeat ▁structures ▁at ▁the ▁N - term inal ▁fl ank ▁of ▁the ▁core ▁repeat ▁array . ▁These ▁structures , ▁term ed ▁non - can on ical ▁or ▁deg ener ate ▁repe ats ▁have ▁been ▁shown ▁to ▁be ▁vital ▁for ▁DNA ▁binding , ▁though ▁all ▁but ▁one ▁do ▁not ▁contact ▁DNA ▁bases ▁and ▁thus ▁make ▁no ▁contribution ▁to ▁sequence ▁preference . ▁The ▁one ▁exception ▁is ▁repeat ▁- 1 , ▁which ▁enc odes ▁a ▁fixed ▁T - zero ▁preference ▁to ▁all ▁T A LE s . ▁This ▁means ▁that ▁the ▁target ▁sequences ▁of ▁T A LE s ▁are ▁always ▁preced ed ▁by ▁a ▁th ym ine ▁base . ▁This ▁is ▁thought ▁to ▁be ▁common ▁to ▁all ▁T A LE s , ▁with ▁the ▁possible ▁exception ▁of ▁Tal C ▁from ▁X anth omon as ▁or y za e ▁p v . ▁or y za e ▁stra in ▁A X O 1 9 4 7 ▁( ). ▁ ▁R ip T AL s ▁ ▁Disc overy ▁and ▁mole cular ▁properties ▁It ▁was ▁noted ▁in ▁the ▁ 2 0 0 2 ▁publication ▁of ▁the ▁gen ome ▁of ▁reference ▁stra in ▁R al st onia ▁sol an ace ar um ▁G MI 1 0 0 0 ▁that ▁its ▁gen ome ▁enc odes ▁a ▁protein ▁similar ▁to ▁X anth omon as ▁T A LE s . ▁Based ▁on ▁similar ▁domain